Polypropylene fibers and fabrics

ABSTRACT

This invention relates to polypropylene fibers and fabrics containing polypropylene fibers, the fibers comprising propylene polymers comprising at least 50 mol % propylene, said polymers having: a) a melt flow rate (MFR, ASTM 1238, 230° C., 2.16 kg) of about 10 dg/min to about 25 dg/min; b) a dimensionless Stress Ratio/Loss Tangent Index R2 [defined by Eq. (8)] at 190° C. from about 1.5 to about 30; c) an onset temperature of crystallization under flow, Tc,rheol, (as determined by SAOS rheology, 190° C., 1° C./min, where said polymer has 0 wt % nucleating agent present), of at least about 123° C.; d) an average meso run length determined by 13C NMR of at least about 55 or higher; and e) optionally, a loss tangent, tan δ, [defined by Eq. (2)] at an angular frequency of 0.1 rad/s at 190° C. from about 14 to about 70.

This application is a continuation of application Ser. No. 13/691,984filed Dec. 3, 2012, U.S. Pat. No. 9,322,114, the entire contents ofwhich is hereby incorporated by reference.

STATEMENT OF RELATED CASES

This application relates to concurrently filed U.S. Patent ApplicationSer. No. 61/732,451 entitled “Propylene Polymers”, assigned toExxonMobil Chemical Patents Inc. Inventors: Jeanne MacDonald, AntoniosK. Doufas, Jerome Sarrazin, William Ferry, Rahul Kulkarni, DerekThurman, Cynthia Mitchell, Detlef Frey, Peter Schlag, Hans-Georg Geus,and Claudio Cinquemani.

FIELD OF THE INVENTION

This invention relates to fibers made from propylene polymers, yarns andfabrics made from the fibers, and articles made from the fibers, yarnsand fabrics. The fibers and fabrics have an excellent combination oftensile and textural properties useful in various applications, such ashygiene products, medical products and consumer products.

BACKGROUND OF THE INVENTION

Polypropylene is conventionally used to produce fibers and spunbondnonwovens for a wide range of articles, such as, for example, disposablehygiene goods including diapers, sanitary napkins, training pants, adultincontinence products, hospital gowns, baby wipes, moist towelettes,cleaner cloths, and the like. The typical polypropylene nonwoven fabriccan mimic the appearance, texture and strength of a woven fabric. Incombination with other materials they provide a spectrum of productswith diverse properties, and are also used alone or as components ofapparel, home furnishings, health care, engineering, industrial andconsumer goods. Conventionally, propylene based materials such aspolypropylene that present excellent spinnability (e.g. stablefabrication without breaks of thin fibers on the order of about 0.7-2denier and particularly about 1-1.5 denier) suffer from poor fiberand/or fabric properties (e.g. low tensile strength/tenacity).Inversely, polypropylene compositions that exhibit acceptablefiber/fabric properties such as good tensile strength have poorprocessability associated with fiber breaks and drips in the spinline,particularly when thin fibers are made (e.g. <20 microns or equivalently<2 denier). Thus, there is a general interest to impart superior tensilestrength in both machine direction (MD) and transverse direction (TD,also referred to as Cross Direction, CD) of polypropylene nonwovenfabrics, while exhibiting excellent processability and spinnability,particularly for applications requiring improved mechanical strengthsuch as disposable hygiene articles.

Likewise, in general, at low fabric basis weights (e.g. <15 g/m²), highline speeds (e.g. >600 m/min) and high throughput rates, conventionalpolypropylene resins do not provide the desired fabric strengthproperties. Thus, it is desirable to develop polypropylene fibers andfabrics that exhibit high fabric strength at low fabric basis weightsand high line speeds. This allows the fabric converter to downgauge thespunbonding process utilizing less polypropylene resin (lower basisweight fabric) without sacrificing fabric mechanical properties. Whenused to prepare low basis weight (less than about 15 g/m²) spunbondfabrics at high line speeds (such as 900 m/min or more), typicalpolypropylene resins tend to show specific tensile strengths (tensilestrength in N per 5 cm fabric width divided by fabric basis weight) ofroughly 1 N/5 cm/gsm or less (where gsm is g/m²) in thetransverse(cross) direction when run in a three beam spunbondingconfiguration.

Additional references of interest include: U.S. Pat. Nos. 7,105,603;6,583,076; 5,723,217; 5,726,103; U.S. Patent Publication Nos.2010/233927; 2011/059668; 2011/081817; 2012/0116338, 2010/0233928;2008/0182940; 2008/0172840; 2009/0022956; PCT Publication Nos. WO2010/087921; WO 2006/044083; WO 2006/118794; WO 2007/024447; WO2005/111282; WO 2001/94462; JP 2007-023398 A (JAPAN POLYCHEM CORP, Feb.1, 2007); and Journal Of Applied Polymer Science, John Wiley and SonsInc., New York, May 2001, Vol. 80, No. 8, pp. 1243-1252. US2012-0116338Adiscloses spunbond fibers made from visbroken polypropylene with a meltflow rate of greater than 50 dg/min. US2010/0233928A discloses fabricscomprising fine meltspun fibers comprising one or more primarypolypropylenes having a molecular weight distribution of less than 3.5and a melt flow rate within the range from 5 to 500 dg/min, the fibershaving at least one of an average diameter of less than 20 μm or adenier (g/9000 m) of less than 2.0.

BRIEF SUMMARY OF THE INVENTION

This invention relates to fibers that have an excellent combination ofproperties, including fiber strength/tenacity, and to nonwoven fabricscomprising the fibers, the fabrics having advantageous tensileproperties and textural properties even at low fabric basis weightstrengths and/or when produced at high production line speeds. Thefibers may be made from propylene polymer compositions having anexcellent combination of rheological, crystallization and tacticityproperties. Certain advantageous nonwoven fabrics of this inventioncomprise propylene polymer fibers composed of a propylene polymercomprising at least 50 mol % propylene, said polymer having:

a) a melt flow rate (MFR, ASTM 1238, 230° C., 2.16 kg) of about 10dg/min to about 21.5 dg/min;

b) a dimensionless Stress Ratio/Loss Tangent Index R₂ [defined by Eq.(8) below] at 190° C. from about 1.5 to about 28;

c) an onset temperature of crystallization under flow, T_(c,rheol), (asdetermined by SAOS rheology, 1° C./min as described below, where saidpolymer has 0 wt % nucleating agent present), of at least about 131° C.;and

d) an average meso run length determined by ¹³C NMR of at least about 97or higher.

The invention also provides a nonwoven fabric having a fabric basisweight of not more than 15 gsm and comprising polypropylene fibershaving a dpf value of 0.3 to 5 dpf, wherein said polypropylene fiberscomprise a propylene polymer composition comprising at least 50 mol %propylene, said polymer composition having:

a) a melt flow rate (MFR, ASTM 1238, 230° C., 2.16 kg) of about 10 to 25dg/min

b) a dimensionless Stress Ratio/Loss Tangent Index R₂ [defined by Eq.(8)] at 190° C. from 1.5 to 30

c) an onset temperature of crystallization under flow, T_(c,rheol), (asdetermined by SAOS rheology, 1° C./min as described below, where saidpolymer has 0 wt % nucleating agent present), of at least about 123° C.and

d) an average meso run length determined by ¹³C NMR of at least about 55or higher.

Advantageously, said fabric is obtainable by spunbonding with aproduction line speed of at least 400 m/min and/or has a fabric tensileanisotropy as defined herein of less than 3.0 when produced at aproduction line speed of 900 m/min.

Furthermore the invention provides a nonwoven fabric having a fabricbasis weight of not more than 15 gsm and comprising polypropylene fibershaving a dpf value of 0.3 to 5 dpf, wherein:

said nonwoven fabric is obtainable by spunbonding with a production linespeed of at least 400 m/min;

said polypropylene fibers comprise a propylene polymer compositioncomprising at least 50 mol % propylene, said polymer composition having:

a) a melt flow rate (MFR, ASTM 1238, 230° C., 2.16 kg) of about 10dg/min to about 40 dg/min;

b) a dimensionless Stress Ratio/Loss Tangent Index R₂ [defined by Eq.(8) herein] at 190° C. from about 0.6 to about 30;

c) an onset temperature of crystallization under flow, T_(c,rheol), (asdetermined by SAOS rheology, 1° C./min as described herein, where saidpolymer has 0 wt % nucleating agent present), of at least about 120° C.;and

d) an average meso run length determined by ¹³C NMR of at least about 65or higher; and said fabric has a ratio of CD elongation to CD peakStrength of 40 or more (when measured at speed of 200 mm/min) and a CDstrength of 1.0 N/5 cm/gsm or more.

Moreover the invention provides a polypropylene fiber comprising apropylene polymer comprising at least 50 mol % propylene, said polymerhaving:

a) a melt flow rate (MFR, ASTM 1238, 230° C., 2.16 kg) of about 10dg/min to about 21.5 dg/min;

b) a dimensionless Stress Ratio/Loss Tangent Index R₂ [defined by Eq.(8) herein] at 190° C. from about 1.5 to about 28;

c) an onset temperature of crystallization under flow, T_(c,rheol), (asdetermined by SAOS rheology, 1° C./min as described herein, where saidpolymer has 0 wt % nucleating agent present), of at least about 131° C.;and

d) an average meso run length determined by ¹³C NMR of at least about 97or higher.

A number of other combinations of rheological, crystallization andtacticity attributes defining the compositions of propylene polymersused in certain illustrative embodiments of the invention are alsodisclosed herein.

In one exemplary embodiment, fibers and fabrics of the invention may bemade from a composition that is a reactor grade propylene polymer or acontrolled rheology (visbroken) propylene polymer The propylene polymersmay be visbroken propylene polymers, which may be obtainable by aprocess comprising contacting a propylene polymer having an MFR of 0.1to 8 dg/min (preferably 0.5 to 6 dg/min, preferably 0.8 to 3 dg/min),with a visbreaking agent (such as peroxide), under conditions sufficientto obtain a propylene polymer having a) an MFR of 10 dg/min or more,preferably from 10 to 25, preferably from 14 to 19 dg/min as furtherdescribed herein.

Fibers of this invention have excellent tensile properties, for exampletensile strength, elongation and flexural modulus. Fabrics made from thefibers have excellent combinations of tensile properties and texturalproperties, for example hand. This invention also relates to spunbondednonwoven fabrics having the desirable combination of high fabricstrength (both in MD and CD directions) at low fabric basis weights(e.g. less than 15 gsm) and high fabric production line speeds (e.g.greater than 400 m/min, especially greater than 600 m/min). The fibersand fabrics of this invention can be manufactured at high line speedswith excellent process ability/spinnability.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts the evolution of the loss tangent (tan δ) under a coolingSAOS rheological experiment.

FIG. 2 depicts the complex viscosity of Examples 1, 3, 10, 12, 13, 14,16, and 18.

DEFINITIONS

An “olefin,” alternatively referred to as “alkene,” is a linear,branched, or cyclic compound of carbon and hydrogen having at least onedouble bond. For purposes of this specification and the claims appendedthereto, when a polymer or copolymer is referred to as comprising anolefin, including, but not limited to ethylene, propylene, and butene,the olefin present in such polymer or copolymer is the polymerized formof the olefin. For example, when a copolymer is said to have a“propylene” content of 35-55 wt %, it is understood that the mer unit inthe copolymer is derived from propylene in the polymerization reactionand said derived units are present at 35-55 wt %, based upon the weightof the copolymer. A “polymer” has two or more of the same or differentmer units. A “homopolymer” is a polymer having mer units that are thesame. A “copolymer” is a polymer having two or more mer units that aredifferent from each other. A “terpolymer” is a polymer having three merunits that are different from each other. The term “different” as usedto refer to mer units indicates that the mer units differ from eachother by at least one atom or are different isomerically. Accordingly,the definition of copolymer, as used herein, includes terpolymers andthe like. A “propylene polymer,” also referred to as “polypropylene,” isa polymer comprising 50 mol % or more units derived from propylene. Anoligomer is typically a polymer having a low molecular weight (such anMn of less than 25,000 g/mol, preferably less than 2,500 g/mol) or a lownumber of mer units (such as 75 mer units or less).

As used herein, the new notation for the Periodic Table Groups is usedas described in Chemical and Engineering News, 63(5), 27 (1985).

As used herein, “metallocene catalyst” means a Group 4 transition metalcompound having at least one cyclopentadienyl, indenyl or fluorenylgroup attached thereto that is capable of initiating olefin catalysis,typically in combination with an activator.

The terms “catalyst” and “catalyst compound” are defined to mean acompound capable of initiating catalysis. In the description herein, thecatalyst may be described as a catalyst precursor, a pre-catalystcompound, or a transition metal compound, and these terms are usedinterchangeably. A catalyst compound may be used by itself to initiatecatalysis or may be used in combination with an activator to initiatecatalysis. When the catalyst compound is combined with an activator toinitiate catalysis, the catalyst compound is often referred to as apre-catalyst or catalyst precursor. A “catalyst system” is a combinationof at least one catalyst compound, an optional activator, an optionalco-activator, and an optional support material, where the system canpolymerize monomers to polymer. For the purposes of this invention andthe claims thereto, when catalyst systems are described as comprisingneutral stable forms of the components, it is well understood by one ofordinary skill in the art, that the ionic form of the component is theform that reacts with the monomers to produce polymers.

As used herein, “fibers” may refer to filaments, yarns, or staplefibers.

A “filament” refers to a monolithic fiber also referred to as a“monofilament” or a “continuous filament”. For the avoidance of doubt,the term “filament” extends to filaments which are formed and laid downas a fabric in a continuous process, for example a as spunbondednonwoven, without intervening isolation of the filaments.

A yarn is an assembly of two or more fibers which are assembled with orwithout twist. Said two or more fibers may be the same or different, butare preferably the same. Fibers used to form a yarn may eachindependently be a filament, may each independently itself be a yarn, ormay be a mixture of filaments and yarns. Many yarns consist of amultiplicity of filaments.

A “filament yarn” (also referred to herein as a “continuous filamentyarn”) is an assembly of at least two filaments which are assembled withor without twist.

“Staple fibers” (also referred to herein as “staple”) are lengths offilament or yarn which have been cut from continuous filament or yarn.Staple fibers will normally have a uniform length. Typical staple fiberlengths are for example up to 500 mm, especially up to 200 mm, forexample a length in the range of from 3 mm to 200 mm.

“Bulked” or “textured” fibers are fibers which have been treated, forexample by crimping or other means, to modify texture in a fabric madefrom the fibers.

In relation to fibers, “partially oriented” refers to spun fibers,especially meltspun fibers, which have been drawn in the melt statewithout solid state drawing, and “fully oriented” refers to fibers whichhave undergone solid state orientation, for example by solid statedrawing. Fibers which are fully oriented may have been, but have notnecessarily been, melt-drawn before they are subjected to solid statedrawing.

“Partially oriented yarns” are spun fibers (which may be a singlefilament or an assembly of more than one filament), especially meltspunfibers, that are partially oriented.

“Fully oriented yarns” are spun fibers (which may be a single filamentor an assembly of more than one filament), especially meltspun fibers,that are fully oriented.

Good spinnability is defined in this invention as no fiber breaks, dripsor hard pieces occurring for a running period of 8 hours at throughputrates in the range of 0.3 to 0.6 ghm (grams per minute per hole) whenforming fibers of about 0.8 to about 5 (preferably 0.8 to about 4,preferably 0.8 to about 2.5, preferably from about 1 to about 1.6)denier for fabrics having a basis weight of 5 to 25 g/m² (preferablyabout 7 to about 20 g/m², preferably about 8 to about 15 g/m²,preferably about 9 to about 11 g/m²). Hard pieces are small plasticaggregates that affect the homogeneity of nonwoven fabric negatively.

For purposes of this invention and the claims thereto, when a polymer isdescribed as having 0 wt % nucleating agent present, it means that noexternal nucleating agents have been added to the polymer. The phrasedoes not mean that the polymer contains no “internal nucleating agents,”i.e. materials that are present in the neat polymer as produced that actas nucleating agents. When a polymer is described as having a certainproperty with 0 wt % nucleating agent present, it means the test isconducted on polymer that has had no external nucleating agents added toit. For example the phrase “having a T_(cp) (measured by DSC at acooling rate of 10° C. per minute) with 0% nucleating agent of at leastabout 123° C. or higher” means that the polymer in question has a T_(cp)of at least about 123° C. or higher when measured on a sample of thepolymer where no external nucleating agents have been added to thepolymer prior to the DSC test. This phrase is not meant to indicate thatnucleating agents may not be added to the polymers as part of the normalproduction process.

In this specification, “production line speed” means, in relation to anonwoven fabric, the linear speed of a web or other surface onto whichfibers are laid down to form the nonwoven fabric and thus essentiallycorresponds to the rate of delivery of the nonwoven fabric from theformation section of a nonwoven fabric formation apparatus.

DETAILED DESCRIPTION

The inventors have surprisingly discovered that fibers made frompropylene based compositions characterized by a unique combination ofspecific melt rheological, crystallization and tacticity molecularparameters exhibit a superior combination of spinnability duringmanufacture and fiber/fabric tensile properties in the fibers per se andin fabrics comprising said fibers. In one embodiment fibers and fabricsare made from compositions having distinct rheological (including meltelasticity) and shear thinning characteristics, differentiated DSC(differential scanning calorimetry) behavior and crystallization underflow kinetics as monitored by rotational rheometry. Contrary to previouspolypropylenes, the preferred compositions from which the fibers of theinvention are obtainable do not require narrow molecular weightdistributions (Mw/Mn) to achieve enhanced spinnability and fiberproperties. Therefore, the compositions do not have to be made withmetallocene catalysts to obtain narrow Mw/Mn, although use ofmetallocene catalysts (and narrow Mw/Mn's) is still feasible as long asthe composition satisfies the defined range of compositional attributesdescribed herein. Certain especially preferred compositions describedherein are those disclosed in U.S. application Ser. No. 61/732,451entitled “Propylene Polymers”, assigned to ExxonMobil Chemical PatentsInc. filed on the same date as the present application, the entiredisclosure of which is incorporated herein by reference. The fibers ofthe invention are advantageously partially oriented yarns, fullyoriented yarns, monofilaments and staple fibers and are particularlyuseful for formation of spunbonded fabrics, melt blown fabrics,combinations of spunbonded and melt blown fabric structures as well aspartially oriented yarns, fully oriented yarns, and staple fibers.

In a preferred embodiment of the invention the fibers and/or fabricscomprise a visbroken propylene polymer, typically obtainable byvisbreaking a propylene polymer having an MFR of about 0.1 to about 8dg/min (preferably 0.6 to 6 dg/min, preferably 0.8 to 3 dg/min) beforeforming said fibers or fabric.

In a preferred embodiment of the invention, the fibers and fabricscomprise a visbroken (controlled rheology) propylene polymer or areactor grade propylene polymer (i.e., a propylene polymer that has notbeen treated to visbreaking) or combinations thereof. In the case of avisbroken propylene composition, the initial polymer before thevisbreaking step will be referred to as the “base polymer”.

Polymer Compositions

In a preferred embodiment of the invention, the inventive propylenepolymer compositions may comprise visbroken (controlled rheology),reactor grade (non visbroken) propylene based polymers and/orcombinations thereof. The inventive propylene polymer compositions arepreferably formed into fibers, webs, molded parts or other shapes.

In certain preferred embodiments this invention relates to fibers andfabrics comprising propylene polymers comprising at least 50 mol %propylene (preferably at least 80 mol % propylene, preferably at least90 mol % propylene, preferably 100 mol % propylene), said polymerhaving:

a) a melt flow rate (MFR, ASTM 1238, 230° C., 2.16 kg) of about 10 toabout 21.5 dg/min (preferably 12 to 22 dg/min, preferably 13 to 20dg/min, preferably 14 to 19 dg/min, preferably 14 to 18 dg/min,preferably 14 to 17 dg/min);

b) a dimensionless Stress Ratio/Loss Tangent Index R₂ [defined by Eq.(8) below] at 190° C. from about 1.5 to about 28 (preferably 2 to 15,preferably 2.5 to 6.5);

c) an onset temperature of crystallization under flow, T_(c,rheol), (asdetermined by SAOS rheology, 1° C./min as described below, where saidpolymer has 0 wt % nucleating agent present), of at least about 131° C.(preferably 133° C. or more, preferably 135° C. or more, preferably 136°C. or more, preferably 137° C. or more); andd) an average meso run length determined by ¹³C NMR of at least about 97or higher (preferably 97 to 150, preferably 100 to 140, preferably 105to 130); and optionallye) a loss tangent, tan δ, [defined by Eq. (2) below] at an angularfrequency of 0.1 rad/s at 190° C. from about 10 to about 70 (preferably14 to about 70, preferably 35 to 65, preferably 45 to 55.

In a preferred embodiment of the invention, the propylene polymer ispropylene homopolymer.

Preferred inventive propylene polymer compositions useful in fibers andfabrics claimed herein include propylene polymers additionally havingone or more of the following properties:

-   1. an Mw of 30,000 to 2,000,000 g/mol, preferably 150,000 to    300,000, more preferably 190,000 to 240,000, as measured by GPC    described in the test methods section; and/or-   2. a Tm (second melt, 1° C./min ramp speed, also referred to as    “T_(mp)”) of 100° C. to 200° C., preferably 110° C. to 185° C.,    preferably 115° C. to 175° C., more preferably 140° C. to 170° C.,    more preferably 155° C. to 167° C., as measured by the DSC method    described below in the test methods; and/or-   3. a percent crystallinity (based on the heat of crystallization) of    20% to 80%, preferably 30% to 70%, more preferably 35% to 55% as    measured by the DSC method described below in the test methods;    and/or-   4. a glass transition temperature, Tg, of −50° C. to 120° C.,    preferably −20° C. to 100° C., more preferably −0° C. to 90° C. as    determined by the DSC method described below in the test methods;    and/or-   5. a crystallization temperature, Tc, (1° C./min ramp speed, also    referred to as “T_(cp)”) determined on a sample having 0 wt %    nucleating agent of 15° C. to 150° C., preferably 110° C. to 150°    C., more preferably 126° C. to 147° C., preferably 129° C. to 139°    C., as measured by the DSC method described below in the test    methods, and/or-   6. a branching index (g′_(vis)) of 0.85 or more, preferably 0.90 or    more, preferably 0.95 or more, preferably 0.99 or more.

In any embodiment of the invention herein, the inventive fibers orfabrics may comprise propylene polymer compositions having an Mw/Mn of 1to 7, preferably 1.2 to 5, more preferably 1.5 to 4, as measured by GPC.

In any embodiment of the invention herein, the inventive fibers orfabrics may comprise propylene polymer compositions having an Mz/Mw of1.5 to 2.5, more preferably 1.8 to 2.2, more preferably 1.9 to 2.1, asmeasured by GPC.

In any embodiment of the invention herein, the inventive fibers orfabrics may comprise propylene polymer compositions having an onsettemperature of crystallization under flow, T_(c,rheol), (determined viaSAOS rheology, 1° C./min, 190° C., where the polymer sample to be testedhas 0% nucleating agent, as described below) of 131° C. or more,preferably 135° C. or more, preferably 136° C. or more, preferably 137°C.

In any embodiment of the invention herein, the inventive fibers orfabrics may comprise propylene polymer compositions having aDimensionless Stress Ratio Index R₁ [defined by Eq. (7) below] at 190°C. of 1.2 to 4.5, preferably 1.8 to 3.6, preferably 2 to 3, asdetermined by the SAOS Rheology method described below in the testmethods section.

In any embodiment of the invention herein, the inventive fibers orfabrics may comprise propylene polymer compositions having aDimensionless Stress Ratio/Loss Tangent Index R₂ [defined by Eq. (8)below] at 190° C. of about 1.5 to about 28, preferably 2 to 15,preferably 2.5 to 6.5, as determined by the SAOS Rheology methoddescribed below in the test methods section.

In any embodiment of the invention herein, the inventive fibers orfabrics may comprise propylene polymer compositions having aDimensionless Shear Thinning Index R₃ [defined by Eq. (9) below] at 190°C. of 6 to 13, preferably 6.5 to 12.5, preferably 7 to 10, as determinedby the SAOS Rheology method described below in the test methods section.

In any embodiment of the invention herein, the inventive fibers orfabrics may comprise propylene polymer compositions having aDimensionless Loss Tangent/Elasticity Index R₄ [defined by Eq. (10)below] at 190° C. of 1.5 to 20, preferably 1.7 to 10.7, preferably 2 to6, as determined by the SAOS Rheology method described below in the testmethods section.

In any embodiment of the invention herein, the inventive fibers orfabrics may comprise propylene polymer compositions having a LossTangent (tan δ) at an angular frequency of 0.1 rad/s [defined by Eq. (2)below] at 190° C. from about 14 to about 70, preferably 35 to 65,preferably 45 to 55, as determined by the SAOS Rheology method describedbelow in the test methods section.

In any embodiment of the invention herein, the inventive fibers orfabrics may comprise propylene polymer compositions having an averagemeso run length [defined by Eq. (16) below] of 97 or higher, preferably100 or higher, preferably 105 or higher, as determined by the ¹³C NMRmethod described below in the test methods section. Alternately, any ofthe inventive fibers or fabrics may comprise propylene polymercompositions having an average meso run length [defined by Eq. (16)below] of 97 to 150, preferably 100 to 140, preferably 105 to 130. Incertain embodiments lower average meso run lengths are possible providedthat the average meso run length is at least 55.

In any embodiment of the invention herein, the inventive fibers orfabrics may comprise propylene polymer compositions having a T_(mp)(second heat, measured by DSC at a heating rate of 1° C. per minute) of120° C. or more, 140° C. or more, preferably 155° C. or more, preferably160° C. or more, as determined by the DSC method described below in thetest methods section.

In any embodiment of the invention herein, the inventive fibers orfabrics may comprise propylene polymer compositions having a T_(mp)(measured by DSC at a heating rate of 10° C. per minute) of 120° C. ormore, preferably 140° C. or more, preferably 155° C. or more, preferably160° C. or more, as determined by the DSC method described below in thetest methods section.

In any embodiment of the invention herein, the inventive fibers orfabrics may comprise propylene polymer compositions having a T_(cp)(measured by DSC at a cooling rate of 1° C. per minute, where thepolymer to be measured has 0 wt % nucleating agent) of 125° C. or more,preferably 126° C. or more, preferably 127° C. or more, preferably 128°C. or more, preferably 129° C., preferably 130° C. or more, preferably133° C. or more, as determined by the DSC method described below in thetest methods section.

In any embodiment of the invention herein, the inventive fibers orfabrics may comprise propylene polymer compositions having a T_(cp)(measured by DSC at a cooling rate of 10° C. per minute, where thepolymer to be tested has 0 wt % nucleating agent) of 115° C. or more,preferably 116° C. or more, preferably 117° C. or more, preferably 118°C. or more, preferably 119° C. or more, preferably 120° C. or more,preferably 121° C. or more, preferably 122° C. or more, preferably 123°C. or more, as determined by the DSC method described below in the testmethods section.

In any embodiment of the invention herein, the composition of which thefibers or fabrics are formed may have a supercooling parameter SPC[defined by Eq. (12) below] (measured by DSC at a heating and coolingrate of 1° C. per minute, where the polymer to be tested has 0%nucleating agent) of −11° C. or less, preferably −15° C. or less orpreferably less than −17° C., as determined by the DSC method asdescribed below in the test methods section.

In any embodiment of the invention herein, the composition may have asupercooling parameter SPC [defined by Eq. (12) below] (measured by DSCat a heating and cooling rate of 10° C. per minute, where the polymer tobe tested has 0% nucleating agent) of about −1° C. or less, preferably−3.5° C. or less, as determined by the DSC method as described below inthe test methods section.

In any embodiment of the invention herein, the inventive fibers orfabrics may comprise propylene polymer compositions having an onsettemperature of crystallization under flow (determined via SAOS rheology,1° C./min) T_(c,rheol), where the polymer to be tested has 0 wt %nucleating agent) of 131° C. or more, preferably 135° C. or more,preferably 136° C. or more, preferably 137° C. or more as determined bythe SAOS Rheology method described below in the test methods section,and a dimensionless Stress Ratio Index R₁ [defined by Eq. (7) below] at190° C. of 1.2 to 4.5, preferably 1.8 to 3.6, preferably 2-3, asdetermined by the SAOS Rheology method described below in the testmethods section.

In any embodiment of the invention herein, the inventive fibers orfabrics may comprise propylene polymer compositions having a T_(mp)(measured by DSC at a heating of 1° C. per minute) of 140° C. or more,preferably 155° C. or more, preferably 160° C. or more, as determined bythe DSC method described below in the Test and Materials section, anddimensionless Stress Ratio Index R₁ [defined by Eq. (7) below] at 190°C. of 1.2 to 4.5, preferably 1.8 to 3.6, preferably 2 to 3, asdetermined by the SAOS Rheology method described below in the testmethods section.

In any embodiment of the invention herein, inventive fibers or fabricsmay comprise propylene polymer compositions having a T_(c,rheol) of 131°C. or more, preferably 135° C. or more, preferably 136° C. or more,preferably 137° C. or more as determined the SAOS Rheology methoddescribed below in the test methods section, and a dimensionless LossTangent/Elasticity Index R₄ [defined by Eq. (10) below] at 190° C. of1.5 to 20, preferably 1.7 to 10.7, preferably 2 to 6, as determined bythe SAOS Rheology method described below in the test methods section.

In any embodiment herein the inventive fibers or fabrics may comprisepropylene polymer compositions having a T_(cp) (measured by DSC at aheating and cooling rate of 1° C. per minute, where the polymer to betested has 0 wt % nucleating agent) of 125° C. or more (preferably 126°C. or more, preferably 127° C. or more, preferably 128° C. or more,preferably 130° C. or more, preferably 133° C. or more), as determinedby the DSC method described below in the Test a section, and aDimensionless Loss Tangent/Elasticity Index R₄ [defined by Eq. (10)below] at 190° C. of 1.50 to 20, preferably 1.7 to 10.7, preferably 2 to6, as determined by the SAOS Rheology method described below in the testmethods section.

In any embodiment of the invention herein, the inventive fibers orfabrics may comprise propylene polymer compositions having a T_(cp)(measured by DSC at a cooling rate of 10° C. per minute, where thepolymer to be measured has 0 wt % nucleating agent) of 115° C. or more,preferably 116° C. or more, preferably 117° C. or more, preferably 118°C. or more, preferably 119° C. or more, preferably 120° C. or more,preferably 122° C. or more, preferably 123° C. or more, as determined bythe DSC method described below in the Test a section, and adimensionless Loss Tangent/Elasticity Index R₄ [defined by Eq. (10)] at190° C. of 1.5 to 20, preferably 1.7 to 10.7, preferably 2 to 6, asdetermined by the SAOS Rheology method described below in the testmethods section.

In any embodiment herein the inventive fibers or fabrics may comprise apropylene polymer composition comprising a propylene based polymerhaving:

-   -   (1) an MFR in the range from about 10 dg/min to about 21.5        dg/min;    -   (2) a Dimensionless Stress Ratio/Loss Tangent Index R₂ [defined        by Eq. (8)] at 190° C. from about 1.5 to about 28;    -   (3) An onset temperature of crystallization under flow        T_(c,rheol) (via SAOS rheology, 1° C./min) with 0% nucleating        agent of at least about 131° C. or higher;    -   (4) an average meso run length determined by ¹³C NMR of at least        about 97 or higher.

In any embodiment herein the inventive fibers or fabrics may comprise apropylene polymer composition comprises a propylene based polymerhaving:

-   -   1) an MFR in the range from about 10 dg/min to about 21.5        dg/min;    -   2) a Loss Tangent (tan δ) at an angular frequency of 0.1 rad/s        [defined by Eq. (2)] at 190° C. from about 14 to about 70;    -   3) An onset temperature of crystallization under flow        T_(c,rheol) (via SAOS rheology, 1° C./min) with 0% nucleating        agent of at least about 131° C. or higher;    -   4) an average meso run length determined by ¹³C NMR of at least        about 97 or higher.        In any embodiment of the invention herein, the inventive        propylene polymer composition comprises a propylene based        polymer having:        1) an MFR in the range from about 10 dg/min to about 21.5        dg/min;        2) a Dimensionless Loss Tangent/Elasticity Index R₄ (defined by        Eq. (10) below) at 190° C. from about 1.5 to about 20;        3) a T_(cp) (measured by DSC at a cooling rate of 1° C. per        minute) with 0% nucleating agent of at least about 125° C. or        higher; and        4) an average meso run length determined by ¹³C NMR of at least        about 97 or higher.

In any embodiment of the invention herein, the inventive fibers orfabrics comprise a propylene based polymer having:

1) an MFR in the range from about 10 dg/min to about 21.5 dg/min; and

a) a Dimensionless Stress Ratio Index R₁ (defined by Eq. (7) below) at190° C. from about 1.2 to about 4.5; or

b) a Dimensionless Stress Ratio/Loss Tangent Index R₂ (defined by Eq.(8) below) at 190° C. from about 1.5 to about 28; or

c) a Dimensionless Shear Thinning Index R₃ (defined by Eq. (9) below) at190° C. from about 6 to about 13; or

d) a Dimensionless Loss Tangent/Elasticity Index R₄ (defined by Eq. (10)below) at 190° C. from about 1.5 to about 20; or

e) a Loss Tangent (tan δ) at an angular frequency of 0.1 rad/s (definedby Eq. (2) below) at 190° C. from about 14 to about 70; or

f) a Stress Ratio (SR) at a shear rate of 500 s⁻¹ (defined by Eq. (6)below) at 190° C. from about 3.1 to about 6.1; and

2) a) an onset temperature of crystallization under flow T_(c,rheol)(via SAOS rheology, 1° C./min) with 0% nucleating agent of at leastabout 131° C. or higher; or

b) a T_(cp) (measured by DSC at a cooling rate of 1° C. per minute) with0% nucleating agent of at least about 125° C. or higher; or

c) a T_(cp) (measured by DSC at a cooling rate of 10° C. per minute)with 0% nucleating agent of at least about 117° C. or higher; or

d) a supercooling parameter SCP (measured by DSC at a heating andcooling rate of 10° C./min) with 0% nucleating agent of less than about−1° C.; or

e) a supercooling parameter SCP (measured by DSC at a heating andcooling rate of 1° C./min) with 0% nucleating agent of less than about−11° C.; and

4) a) an average meso run length determined by ¹³C NMR of at least about97 or higher; or

b) a total number of defects (stereo and regio) per 10,000 monomers ofless than about 103.

In another preferred embodiment of the invention, the inventive fibersor fabrics comprise a propylene polymer composition having:

1) an MFR in the range from about 14 dg/min to about 19 dg/min; and

2) a) a Dimensionless Stress Ratio Index R₁ (defined by Eq. (7) below)at 190° C. from about 2.0 to about 3.0; or

b) a Dimensionless Stress Ratio/Loss Tangent Index R₂ (defined by Eq.(8) below) at 190° C. from about 2.5 to about 6.5; or

c) a Dimensionless Shear Thinning Index R₃ (defined by Eq. (9) below) at190° C. from about 7.0 to about 10.0; or

d) a Dimensionless Loss Tangent/Elasticity Index R₄ (defined by Eq. (10)below) at 190° C. from about 2.0 to about 6.0; or

e) a Loss Tangent (tan δ) at an angular frequency of 0.1 rad/s (definedby Eq. (2) below) at 190° C. from about 35 to about 65; or

f) a Stress Ratio (SR) at a shear rate of 500 s⁻¹ (defined by Eq. (6)below) at 190° C. from about 3.3 to about 4.0; and

3) a) an onset temperature of crystallization under flow T_(c,rheol)(via SAOS rheology, 1° C./min) with 0% nucleating agent of at leastabout 134° C. or higher; or

b) a T_(cp) (measured by DSC at a cooling rate of 1° C. per minute) with0% nucleating agent of at least about 133° C. or higher; or

c) a T_(cp) (measured by DSC at a cooling rate of 10° C. per minute)with 0% nucleating agent of at least about 123° C. or higher; or

d) a supercooling parameter SCP (measured by DSC at a heating andcooling rate of 10° C./min) with 0% nucleating agent of less than about−3.5° C.; or

e) a supercooling parameter SCP (measured by DSC at a heating andcooling rate of 1° C./min) with 0% nucleating agent of less than about−17.0° C.; and

4) a) an average meso run length determined by ¹³C NMR of at least about100 or higher; or

b) a total number of defects (stereo and regio) per 10,000 monomers ofless than about 100.

Propylene polymer compositions useful in the inventive fibers or fabricsherein include polypropylene homopolymers, polypropylene copolymers,impact copolymer polypropylenes and blends thereof. The homopolymer maybe isotactic polypropylene, syndiotactic polypropylene or blendsthereof, including blends with atactic polymer. The copolymer can be arandom copolymer, a statistical copolymer, a block copolymer, or blendsthereof. The method of making the propylene polymers is not critical, asthey can be made by slurry, solution, gas phase, a supercriticalpolymerization process as the one described in U.S. Pat. No. 7,807,769,a super-solution homogeneous polymerization process as the one describedin US Patent Application Publication No. 2010/0113718 or other suitableprocesses, and by using catalyst systems appropriate for thepolymerization of polyolefins, such as Ziegler-Natta-type catalysts,metallocene-type catalysts, other appropriate catalyst systems orcombinations thereof. Such catalysts are well known in the art, and aredescribed in, for example, ZIEGLER CATALYSTS (Gerhard Fink, RolfMülhaupt and Hans H. Brintzinger, Eds., Springer-Verlag 1995); Resconiet al., Selectivity in Propene Polymerization with MetalloceneCatalysts, 100 CHEM. REV. 1253-1345 (2000); and I, II METALLOCENE-BASEDPOLYOLEFINS (Wiley & Sons 2000). In a preferred embodiment usefulpropylene polymers are made by the catalysts, activators and processesdescribed in U.S. Pat. No. 6,342,566; U.S. Pat. Nos. 6,384,142;5,741,563; and PCT Publication Nos. WO 03/04020, and WO 97/19991 US. Inanother preferred embodiment, the catalysts described in U.S. Pat. No.7,807,769 and US Patent Application Publication No. 2010/0113718 areuseful to make propylene polymers useful herein.

In a preferred embodiment, the propylene polymer compositions of whichthe inventive fibers or fabrics are composed can be a unimodal reactorgrade, a bimodal reactor grade, an in-reactor blend or an extruder blendof two or more propylene polymers (for example a blend of MFR's of 36dg/min and 2 dg/min) In another embodiment the propylene polymercompositions may have a unimodal, bimodal, or multimodal molecularweight distribution (Mw/Mn) distribution of polymer species asdetermined by GPC. By bimodal or multimodal is meant that the GPC-SECtrace has more than one peak or inflection point. An inflection point isthe point where the second derivative of the curve changes in sign(e.g., from negative to positive or vice versus).

The composition used in the fibers or fabrics of the present inventionadvantageously presents favorable physical properties of molded partsincluding high stiffness (flexural modulus), high tensile strength atyield, high yield strain and high heat distortion temperature evenwithout the use of a nucleating agent. In another embodiment, thepropylene polymer composition has a 1% secant flexural modulusdetermined by ASTM D790A (with 0% nucleating agent) of about 190 kpsi orhigher, preferably greater than about 200 kpsi, preferably greater thanabout 210 kpsi.

In another embodiment of the invention, the propylene polymercomposition has a yield stress determined by ASTM 638 (with 0%nucleating agent) greater than about 4,700 psi, preferably greater thanabout 5,000 psi, preferably greater than about 5,100 psi. In anotherembodiment of the invention, the composition has a yield straindetermined by ASTM638 (with 0% nucleating agent) greater than about 7%,preferably greater than about 8% psi and, preferably greater than about9%.

In another embodiment of the invention, the propylene polymercomposition has a tensile strength at yield of about 4,700 psi orhigher, preferably greater than about 5,000 psi, preferably greater thanabout 5,100 psi (as determined by ASTM 638 with 0 wt % nucleatingagent).

In another embodiment of the invention, the composition of which theinventive fibers or fabrics are composed may have a heat distortiontemperature at 66 psi determined by ASTM D 648 (with 0% nucleatingagent) of about 95° C. or more, preferably greater than about 98° C.,preferably greater than about 100° C., preferably greater than about105° C.

Polymer microstructure is determined by ¹³C-NMR spectroscopy asdescribed in the test methods section below, including the concentrationof isotactic and syndiotactic diads ([m] and [r]), triads ([mm] and[rr]), and pentads ([mmmm] and [rrrr]). The designation “m” or “r”describes the stereochemistry of pairs of contiguous propylene groups,“m” referring to meso and “r” to racemic. The polymers present inpropylene polymer composition useful in the fibers or fabrics of thepresent invention have some level of tacticity. Preferably, the polymerspresent in propylene polymer composition useful in the present inventionhave some level of isotacticity. Thus, in one embodiment of theinvention, isotactic polypropylene is used in the propylene polymercompositions for the inventive fibers or fabrics. Similarly, highlyisotactic polypropylene may be used in another embodiment of theinventive fibers or fabrics. As used herein, “isotactic” is defined ashaving at least 10% isotactic pentads according to analysis by ¹³C-NMR.As used herein, “highly isotactic” is defined as having at least 60%isotactic pentads according to analysis by ¹³C-NMR. In anotherembodiment of the invention, the composition comprising the fibers orfabrics may have an average meso run length MRL [defined by Eq. (16)below] as determined by ¹³C NMR (described in the Tests section) ofhigher than about 97, preferably higher than about 100, preferablyhigher than about 105, preferably 97 to 150, preferably 100 to 140,preferably 105 to 130.

In another embodiment of the invention, the polymer used in thepropylene polymer compositions comprising the fibers or fabrics issyndiotactic, preferably highly syndiotactic. As used herein,“syndiotactic” is defined as having at least 10% syndiotactic pentadsaccording to analysis by ¹³C-NMR. As used herein, “highly syndiotactic”is defined as having at least 60% syndiotactic pentads according toanalysis by ¹³C-NMR.

In another embodiment of the invention, the propylene polymercompositions may comprise a blend of a tactic polymer with an atacticpropylene polymer. Atactic polypropylene is defined to be less than 10%isotactic or syndiotactic pentads. Preferred atactic polypropylenestypically have an Mw of 10,000 up to 1,000,000 g/mol.

Useful propylene polymers for the manufacture of fibers or fabricsherein include those produced by metallocene catalyst systems includingthose propylene polymers having a composition distribution breadth index(CDBI) of 60% or more, preferably 70% or more, preferably 80% or more,preferably 90% or more. (CDBI is measured as described in WO 93/03093,with the modification that any fractions having a weight averagemolecular weight (Mw) below 25,000 g/mol are disregarded.)

In another embodiment of the invention, the inventive fibers or fabricsmay be of a blend of a propylene polymer compositions, for example apolymer as defined herein having at least 50 mol % propylene with a MFRof 10 to 21.5 dg/min may be further blended with any polypropylenedescribed herein, such as a homopolypropylene having an MFR of 22 dg/minor more, preferably 20 to 30 dg/min, preferably 22 to 28 dg/min,preferably about 25 dg/min. The propylene polymer compositions with aMFR of 10 to 21.5 dg/min may be present in such blends at from 1 wt % to99 wt %, based upon the weight of the blend, preferably 5 wt % to 50 wt%, preferably 5 wt % to 25 wt %. Preferably the homopolypropylene havingan MFR of 22 dg/min or more is present in the blend at 99 wt % to 1 wt%, based upon the weight of the blend (preferably at 95 to 50 wt %,preferably at 95 to 75 wt %) and the propylene polymer composition witha MFR of 10 to 21.5 dg/min is present in the blend at from 1 wt % to 99wt %, based upon the weight of the blend, preferably 5 wt % to 50 wt %,preferably 5 wt % to 25 wt %.

Propylene Polymers Useful for Visbreaking

In a preferred embodiment of the invention the fibers or fabricscomprise a propylene polymer composition produced by visbreaking a basepropylene polymer having an MFR of about 0.1 to about 8 dg/min Basepropylene polymers useful herein to produce the visbroken polymersinclude polypropylene homopolymers, polypropylene copolymers, and blendsthereof. The homopolymer may be isotactic polypropylene, syndiotacticpolypropylene or blends thereof (including blends with atacticpolypropylene). The copolymer can be a random copolymer, a statisticalcopolymer, a block copolymer, or blends thereof. The method of makingthe base propylene polymer is not critical, as it can be made by slurry,solution, gas phase, a supercritical polymerization process as the onedescribed in U.S. Pat. No. 7,807,769, a super-solution homogeneouspolymerization process as the one described in US Patent ApplicationPublication No. 2010/0113718 or other suitable processes, and by usingcatalyst systems appropriate for the polymerization of polyolefins, suchas Ziegler-Natta-type catalysts, metallocene-type catalysts, otherappropriate catalyst systems or combinations thereof. Such catalysts arewell known in the art, and are described in, for example, ZIEGLERCATALYSTS (Gerhard Fink, Rolf Mülhaupt and Hans H. Brintzinger, Eds.,Springer-Verlag 1995); Resconi et al., Selectivity in PropenePolymerization with Metallocene Catalysts, 100 CHEM. REV. 1253-1345(2000); and I, II METALLOCENE-BASED POLYOLEFINS (Wiley & Sons 2000). Ina preferred embodiment the base propylene polymers are made by thecatalysts, activators and processes described in U.S. Pat. Nos.6,342,566, 6,384,142, and 5,741,563; and PCT Publication Nos. WO03/040201 and WO 97/19991.

In a preferred embodiment, the base propylene polymer can be a unimodalreactor grade, a bimodal reactor grade, an in-reactor blend or anextruder blend of two or more propylene polymers (for example a blend ofMFR's of 0.8 dg/min and 2 dg/min). The base polymer may have a unimodal,bimodal, or multimodal molecular weight distribution (Mw/Mn)distribution of polymer species as determined by GPC. By bimodal ormultimodal is meant that the GPC-SEC trace has more than one peak orinflection point. An inflection point is that point where the secondderivative of the curve changes in sign (e.g., from negative to positiveor vice versus). Typically the base polymer is visbroken to a final MFRpreferably in the range of 10 to 25 dg/min, more preferably 14 to 19dg/min. In another embodiment of the invention, the base polymer may notrequire peroxide cracking for increase of the MFR, as long as thein-reactor base polymer has desirable MFR (e.g. in the range of 10 to 25dg/min and rheological characteristics). The composition could also bean extruder blend of two or more propylene polymers with or withoutperoxide cracking step, as long as combination of the key meltrheological parameters, crystallization and tacticity attributes aresatisfied.

Preferred base propylene polymers useful to make the visbroken polymerfor use in the fibers and fabrics of this invention typically have:

-   1. an Mw of 240,000 to 2,000,000 g/mol preferably 265,000 to    800,000, more preferably 300,0000 to 600,000, as measured by the GPC    method described in the tests method section; and/or-   2. an Mw/Mn of 1 to 25, preferably 1.6 to 15, more preferably 2 to    8, more preferably 3 to 6 as measured by the GPC method described in    the tests method section; and/or-   3. a Tm (second melt, 1° C./min ramp speed, also referred to as    “T_(mp)”) of 100° C. to 200° C., preferably 120° C. to 185° C.,    preferably 130° C. to 175° C., more preferably 140° C. to 170° C.,    even more preferably 155° C. to 167° C., as measured by the DSC    method described below in the test methods; and/or; and/or-   4. a percent crystallinity (based on the heat of crystallization) of    20% to 80%, preferably 10% to 70, more preferably 35% to 55% as    measured by the DSC method described below in the test methods;    and/or-   5. a glass transition temperature (Tg) of −50° C. to 120° C.,    preferably −20° C. to 100° C., more preferably −0° C. to 90° C. as    determined by the DSC method described below in the test methods;    and/or-   6. a crystallization temperature (Tc 1° C./min ramp speed, also    referred to as “T_(cp)”) with 0% nucleating agent of 50° C. to 170°    C., preferably 100° C. to 150° C., more preferably 110° C. to 145°    C., preferably 115° C. to 135° C., as measured by the DSC method    described below in the test methods; and/or-   7. a branching index (g′_(vis)) of 0.85 or more, preferably 0.90 or    more, preferably 0.95 or more, preferably 0.99 or more, as measured    by the GPC method described in the test methods section; and/or-   8. an MFR (ASTM 1238, 230° C., 2.16 kg) of 0.1 to 8 dg/min,    preferably 0.5 to 5 dg/min, more preferably 0.8 to 3 dg/min), and/or-   9. at least 10% tacticity (e.g. at least syndiotactic or at least    10% isotactic).

The base propylene homopolymer or propylene copolymer useful in thefibers and fabrics of the present invention preferably has some level ofisotacticity. Thus, in one embodiment of the invention, isotacticpolypropylene is used as the base propylene polymer herein. Similarly,highly isotactic polypropylene may be used in another embodiment as thebase polymer. In another embodiment of the invention, the base propylenepolymer may have an average meso run length MRL [defined by Eq. (16)below] as determined by ¹³C NMR (described in the test methods section)of higher than about 50, more preferably higher than about 80, morepreferably higher than about 100, more preferably higher than about 105.

In another embodiment of the invention, the base propylene polymeruseful herein is syndiotactic, preferably highly syndiotactic. As usedherein, “syndiotactic” is defined as having at least 10% syndiotacticpentads according to analysis by ¹³C-NMR. As used herein, “highlysyndiotactic” is defined as having at least 60% syndiotactic pentadsaccording to analysis by ¹³C-NMR.

In another embodiment of the invention, the base propylene polymeruseful herein may comprise a blend of a tactic polymer (such asisotactic polypropylene or highly isotactic polypropylene) with anatactic propylene polymer. Atactic polypropylene is defined to be lessthan 10% isotactic or syndiotactic pentads. Useful atacticpolypropylenes typically have an Mw of 10,000 up to 1,000,000 g/mol.

Base propylene polymers useful herein include those produced bymetallocene catalyst systems including those propylene polymers having acomposition distribution breadth index (CDBI) of 60% or more, preferably70% or more, preferably 80% or more, preferably 90% or more. (CDBI ismeasured as described in WO 93/03093, with the modification that anyfractions having a weight average molecular weight (Mw) below 25,000g/mol are disregarded.)

Visbreaking/Chain Scission

The terms “visbreaking” and “chain scission” are used interchangeablyand are defined as the process of using one or more free radicalinitiators to increase polymer melt flow rate (MFR). This is describedin U.S. Pat. No. 6,747,114 which is incorporated here by reference inits entirety. A “free radical initiator” is defined as a molecularfragment having one or more unpaired electrons.

In the context of this specification a polymer undergoes chain scissionwhen the base polymer, or a blend of polymers, is treated with a freeradical initiator, e.g., peroxide, preferably while the polymer is in amelted state, more preferably in a fully melted state. Preferably, thechain scission is controlled. For example, when a free radical initiatoris used, free radicals of the polymers being treated are produced bythermal scission of the peroxide. Other sources of free radicals such asdiazo compounds, oxygen or other compounds may also be utilized. In anycase, it is contemplated that the free radicals produced from theinitiator (e.g., peroxide) abstract the tertiary hydrogen on thepropylene residue of the polymer. The resulting free radicaldisproportionates to two lower molecular weight chains, one with anolefin near the terminus and the other a saturated polymer. This processcan continue with the generation of successively lower molecular weightpolymers. Thus, under the appropriate conditions, chain scission isinitiated to cause controlled degradation of the polymer or polymerblend.

Crosslinking is a competing process that may occur during chainscission. In a crosslinking reaction, the free radicals combine to formbranched macromolecules of higher molecular weight. Eventually, thissynthesis reaction may lead to vulcanization of the polymer. Incopolymers of ethylene and propylene, this balance of crosslinking anddegradation is mainly dependent on the composition of the copolymer.Since the degradation reaction is uniquely associated with the propyleneresidues, lower amounts of propylene in the copolymer tend to favorcrosslinking over degradation. However, it should be recognized that thescission and crosslinking reactions are not mutually exclusionary. Thatis, even during degradation, some amount of branching may occur. In somecases the branching and scission reactions are random and do not lead toan increase in Mw/Mn. The amount of branching depends on a number ofvariables, primarily the reaction conditions, and the composition of thepolymers and the extent of degradation. Random copolymers having ahigher ethylene content should generate a higher level of branching thanthose with a lower ethylene content. Thus, the rate or extent ofdegradation may be substantially proportional to the relative amounts ofpropylene and ethylene sites. For example, if too many ethylene sitesare present, the use of the peroxide or other free radical initiator mayresult in crosslinking rather than chain scission, and the materialbeing treated will not degrade to a higher MFR. Thus, an importantaspect of certain specific embodiments of the fibers and fabrics of thisinvention relates to the relative amounts of the polymers used in theblend. In blends of the base propylene polymers, these degradationprocesses occur for both of the polymers independently of each other.

The free-radical initiator, e.g., peroxide, may be added to the polymerwhile the polymer is in a solid form, e.g., by coating polymer pelletswith an initiator, such as peroxide, which may be in powder, liquid, orother form, in which case the polymer is said to be “treated” with theinitiator when the initiator becomes active, which usually happens at atemperature higher than melting point of the polymer. Preferably,however, the free-radical initiator is added to the polymer after thepolymer has formed, but while the polymer is in a melted condition,e.g., during the post-polymerization processing, such as when a polymermixture (which may include solvent) is introduced to a devolatalizer orextruder, which typically occurs at an elevated temperature.)

The term “melted” refers to the condition of the polymer when anyportion of the polymer is melted, and includes fully melted andpartially melted. Preferably, the polymer is treated by free-radicalinitiator while the temperature of the polymer is above its meltingpoint.

In one method the visbreaking agent may be a peroxide, and an organicperoxide in another embodiment, wherein at least a methyl group orhigher alkyl or aryl is bound to one or both oxygen atoms of theperoxide. In yet another method, the visbreaking agent may be asterically hindered peroxide, wherein the alkyl or aryl group associatedwith each oxygen atom is at least a secondary carbon, a tertiary carbonin another embodiment. Non-limiting examples of sterically hinderedperoxides (“visbreaking agents”) include2,5-bis(tert-butylperoxy)-2,5-dimethylhexane,2,5-dimethyl-2,5-bis-(t-butylperoxy)-hexyne-3,4-methyl-4-t-butylperoxy-2-pentanone,3,6,6,9,9-pentamethyl-3-(ethylacetate)-1,2,4,5-textraoxy cyclononane,and α,α′-bis-(tert-butylperoxy)diisopropyl benzene, and mixtures ofthese and any other secondary- or tertiary-hindered peroxides. Apreferred peroxide is 2,5-bis(tert-butylperoxy)-2,5-dimethyl-hexane alsoknown with the commercial name: Luperox 101 or Trigonox 101. Luperox 101or Trigonox 101 can be fed in the extruder pure in liquid form or as amasterbatch blend in mineral oil (e.g. 50/50 weight/weight blend ofTrigonox 101/mineral oil). Another common peroxide used as a visbreakingagent for polypropylene is di-t-amyl peroxide most commonly known withthe commercial name DTAP. Alternatively, the free radical initiator mayinclude a diazo compound, or any other compound or chemical thatpromotes free radicals in an amount sufficient to cause degradation asspecified herein.

Preferred propylene polymers useful in the fibers and fabrics of thisinvention, include those that have been treated with a visbreaking agentsuch that its MFR is increased by at least 10%, preferably by at least50% preferably by at least 100%, preferably by at least 300%, preferablyby at least 500%, preferably by at least 650%. In the event the polymeris a blend of different propylene polymers, then an average MFR based onthe logarithmic weight blending rule (Robeson, L. M., “Polymer Blends”,Carl Hanser Verlag, Munich 2007, Chapter 6, p. 368) of the MFRs of theindividual blend components is used to determine the MFR of the blendand was found to lead to excellent estimation of the blend MFR of thestudied systems. For example, for a two component system, the ln(meltflow rate of the blend)=(weight fraction of component 1×ln(melt flowrate of component 1)+weight fraction of component 2×ln(melt flow rate ofcomponent 2). In another embodiment the visbroken polymer has an MFRthat is from 10 to 25 units (dg/min) higher than the base polymer usedto make the visbroken polymer, preferably 12 to 22 dg/min, preferably 14to 19 dg/min.

Additives

A variety of additives may be incorporated into the polymers and polymerblends described above used to make the fibers and fabrics for variouspurposes. Such additives include, for example, stabilizers,antioxidants, fillers, colorants, nucleating agents and slip additives.Primary and secondary antioxidants include, for example, hinderedphenols, hindered amines, and phosphates. Nucleating agents include, forexample, sodium benzoate, talc and other chemicals. Also, othernucleating agents may also be employed such as Ziegler-Natta olefinproduct or other highly crystalline polymer. Other additives such asdispersing agents, for example, Acrowax C, can also be included. Slipagents include, for example, oleamide and erucamide. Catalystdeactivators are also commonly used, for example, calcium stearate,hydrotalcite, calcium oxide, acid neutralizers, and other chemicalsknown in the art.

Other additives may include, for example, fire/flame retardants,plasticizers, curative agents, curative accelerators, cure retarders,processing aids, tackifying resins, and the like. The aforementionedadditives of may also include fillers and/or reinforcing materials,either added independently or incorporated into an additive. Examplesinclude carbon black, clay, talc, calcium carbonate, mica, silica,silicate, combinations thereof, and the like. Other additives which maybe employed to enhance properties include antiblocking agents,lubricants, and nucleating agents. The lists described herein are notintended to be inclusive of all types of additives which may be employedwith the present invention.

It is known that in the making of some meltspun fibers, surfactants andother active agents can be included in the polymer that is to bemelt-processed. By way of example only, U.S. Pat. Nos. 3,973,068 and4,070,218 teach a method of mixing a surfactant with the polymer andthen melt-processing the mixture to form the desired fabric. The fabricis then treated in order to force the surfactant to the surface of thefibers. This is often done by heating the web on a series of heatedrolls and is often referred to as “blooming” As a further example, U.S.Pat. No. 4,578,414 describes wettable olefin polymer fibers formed froma composition comprising a polyolefin and one or more surface-activeagents. The surface-active agents are stated to bloom to the fibersurfaces where at least one of the surface-active agents remainspartially embedded in the polymer matrix. In this regard, the permanenceof wettability can be better controlled through the composition andconcentration of the additive package. Still further, U.S. Pat. No.4,923,914 to Nohr et al. teaches a surface-segregatable, melt-extrudablethermoplastic composition suitable for processing by melt extrusion toform a fiber or film having a differential, increasing concentration ofan additive from the center of the fiber or film to the surface thereof.The differential, increasing concentration imparts the desiredcharacteristic, e.g., hydrophilicity, to the surface of the fiber. As aparticular example in Nohr, polyolefin fiber nonwoven webs are providedhaving improved wettability utilizing various polysiloxanes.

Of course, the particular active agent or agents included within one ormore of the components can be selected as desired to impart or improvespecific surface characteristics of the fiber and thereby modify theproperties of the fabric made there from. A variety of active agents orchemical compounds have heretofore been utilized to impart or improvevarious surface properties including, but not limited to, absorbency,wettability, anti-static properties, anti-microbial properties,anti-fungal properties, liquid repellency (e.g. alcohol or water) and soforth. With regard to the wettability or absorbency of a particularfabric, many fabrics inherently exhibit good affinity or absorptioncharacteristics for only specific liquids. For example, polyolefinnonwoven webs have heretofore been used to absorb oil or hydrocarbonbased liquids. In this regard, polyolefin nonwoven wipes are inherentlyoleophilic and hydrophobic. Thus, polyolefin nonwoven fabrics can betreated in some manner in order to impart good wetting characteristicsor absorbency for water or aqueous solutions or emulsions. As anexample, exemplary wetting agents that can be melt-processed in order toimpart improved wettability to the fiber include, but are not limitedto, ethoxylated silicone surfactants, ethoxylated hydrocarbonsurfactants, ethoxylated fluorocarbon surfactants and so forth. Inaddition, exemplary chemistries useful in making melt-processedthermoplastic fibers more hydrophilic are described in U.S. Pat. Nos.3,973,068 and 4,070,218 to Weber et al. and U.S. Pat. No. 5,696,191 toNohr et al.; the entire contents of the aforesaid references areincorporated herein by reference.

In a further aspect, it is often desirable to increase the barrierproperties or repellency characteristics of a fabric for a particularliquid. As a specific example, it is often desirable in infectioncontrol products and medical apparel to provide a fabric that has goodbarrier or repellency properties for both water and alcohol. In thisregard, the ability of thermoplastic fibers to better repel water oralcohol can be imparted by mixing a chemical composition having thedesired repellency characteristics with the thermoplastic polymer resinprior to extrusion and thereafter melt-processing the mixture into oneor more of the segments. The active agent migrates to the surface of thepolymeric component thereby modifying the surface properties of thesame. In addition, it is believed that the distance or gap betweencomponents exposed on the outer surface of the fiber containingsignificant levels of active agent is sufficiently small to allow theactive agent to, in effect, modify the functional properties of theentire fiber and thereby obtain a fabric having the desired properties.Chemical compositions suitable for use in melt-extrusion processes andthat improve alcohol repellency include, but are not limited to,fluorochemicals. Exemplary melt-processable liquid repellency agentsinclude those available from DuPont under the trade name ZONYLfluorochemicals and also those available from 3M under the tradedesignation FX-1801. Various active agents suitable for impartingalcohol repellency to thermoplastic fibers are described in U.S. Pat.No. 5,145,727 to Potts et al., U.S. Pat. No. 4,855,360 to Duchesne etal., U.S. Pat. No. 4,863,983 to Johnson et al., U.S. Pat. No. 5,798,402to Fitzgerald et al., U.S. Pat. No. 5,459,188 and U.S. Pat. No.5,025,052; the entire contents of the aforesaid references areincorporated herein by reference. In addition to alcohol repellency,chemical compositions can be used to similarly improve the repellency orbarrier properties for other low surface tension liquids. The aboveadditives may be useful in fibers and fabrics of the invention to impartabove discussed advantageous properties.

Inventive fibers and fabrics may further incorporate the residues ofprocessing additives or excipients, for example, process oils orplasiticizers used to facilitate or improve processing of the polymersor polymer blends.

In manufacture of the fibers and fabrics, the blends of polymercompositions and additives may be prepared by any procedure thatguarantees an intimate mixture of the components. For example, thecomponents can be combined by melt pressing the components together on aCarver press to a thickness of 0.5 millimeter (20 mils) and atemperature of 180° C., rolling the resulting slab, folding the endstogether and repeating the pressing, rolling, and folding operation 10times. Internal mixers are particularly useful for solution or meltblending. Blending at a temperature of 180° C. to 240° C. in a BrabenderPlastograph for 1 to 20 minutes has been found satisfactory. Stillanother method that may be used for admixing the components involvesblending the polymers in a Banbury internal mixer above the fluxtemperature of all of the components, e.g., 180° C. for 5 minutes. Theseprocesses are well known in the art and include single and twin screwmixing extruders, static mixers for mixing molten polymer streams of lowviscosity, and impingement mixers.

The blends may be prepared by any procedure that produces a mixture ofthe components, e.g., dry blending, melt blending, etc. In certainembodiments, a complete mixture of the polymeric components is indicatedby the uniformity of the morphology of the dispersion of the polymercomponents.

Melt blend: Continuous melt mixing equipment are generally used. Theseprocesses are well known in the art and include single and twin screwcompounding extruders as well as other machines and processes, designedto homogenize the polymer components intimately.

Dry blend: The polymers and other component may be dry blended and feddirectly into the fiber or nonwoven process extruders. Dry blending isaccomplished by combining polymers and other ingredients in dry blendingequipment. Such equipment and processes are well known in the art andinclude a drum tumbler, a double cone blender, etc. In this case,polymer and other ingredients are melted and homogenized in the processextruder similar to the melt blend process. Instead of making thepellets, the homogenized molten polymer is delivered to the die orspinneret to form the fiber, fabric, film, sheet or molded article.

Fiber and Fabric Formation

The formation of nonwoven fabrics from polyolefins and their blendsgenerally requires the manufacture of fibers by extrusion followed byconsolidation or bonding. The extrusion process is typically accompaniedby mechanical or aerodynamic drawing of the fibers. The fabric of thepresent invention may be manufactured by any technique known in the art.Such methods and equipment are well known. For example, spunbondnonwoven fabrics may be produced by spunbond nonwoven production linesproduced by Reifenhauser GmbH & Co., of Troisdorf, Germany. Thisutilizes a slot drawing technique as described in U.S. Pat. No.4,820,142, EP 1340 843 A1 or U.S. Pat. No. 6,918,750. Additional usefulmethods include those disclosed in US 2012/0116338 A1 and US2010/0233928 A1.

Illustrative fabric basis weights of the fabrics of the invention are inthe range of 5 to 70 gsm, preferably from 5 to 50 gsm, preferably from 5to 25 gsm, more preferably from 5 to 20 gsm, especially from 5 to 15gsm, more preferably 7 to 15 gsm, for example 12 gsm.

In certain embodiments fabrics of the invention as defined in any claimherein have any one or more of the following:

a tensile strength anisotropy defined as the ratio of the specifictensile strength in the MD over the specific tensile strength in the CDof less than about 2.7;

a total hand of less than about 6.8 gr;

a MD tensile modulus (as defined herein) of less than about 35 N/5cm/gsm;

a CD specific tensile strength of at least 1.0 N/5 cm/gsm, preferably atleast 1.1N/5 cm/gsm, a MD specific tensile strength of at least 2.7 N/5cm/gsm, preferably at least 2.9 N/5 cm/gsm, and a total hand of lessthan about 6.8 gm force, preferably less than about 6.6 gm force, or atensile modulus of less than about 32 N/5 cm/gsm, preferably less thanabout 30 N/5 cm/gsm;a fabric tensile anisotropy (ratio of MD over CD specific tensilestrength as defined herein) of less than about 2.7;

In one advantageous embodiment, the nonwoven fabric comprisespolypropylene fibers of a propylene polymer having:

a) a melt flow rate (MFR, ASTM 1238, 230° C., 2.16 kg) of about 14dg/min to about 19 dg/min;

b) a dimensionless Stress Ratio/Loss Tangent Index R₂ [defined by Eq.(8) herein] at 190° C. from about 2.5 to about 6.5;

c) an onset temperature of crystallization under flow, T_(c,rheol), (asdetermined by SAOS rheology, 1° C./min as described below, where saidpolymer has 0 wt % nucleating agent present), of at least about 136° C.;and

d) an average meso run length determined by ¹³C NMR of from 97 to 140.

In certain preferred fabrics of the invention the fibers have a dpfvalue of from 0.3 to 5 dpf. The polypropylene fibers of the fabrics ofthe invention are preferably monofilaments, which preferably have adenier value of from 0.3 to 5 denier.

Nonwoven fabrics of the invention may comprise a single layer or aplurality of layers, for example a plurality of nonwoven layers that arebonded together. The fabrics of the invention may be for examplespunbonded nonwovens or meltblown nonwovens, with spunbonded nonwovensbeing especially preferred. Where a nonwoven fabric of the invention isused in a laminate with one or more other fabric, the other fabric orfabrics may be a fabric of this invention or may be another fabric. Theinvention provides in particular a laminate comprising a plurality ofnonwoven fabrics according to the present invention, which may ifdesired be bonded together. Laminates may include a plurality ofnonwovens selected from spunbonded nonwovens and meltblown nonwovensoptionally with one or more further fabrics. The fabrics may be usedalone or in combination with other fabrics in a wide variety ofapplications as hereinafter described.

As already mentioned the polypropylene fibers of the fabrics of theinvention comprise a propylene polymer comprising at least 50 mol %propylene. It is preferred that the said propylene polymer comprises atleast 60 mol %, preferably at least 70 mol %, more preferably at least80 mol %, for example at least 90 mol % units derived from propylene.Further, fabrics of the invention may if desired comprise fibers of apropylene polymer composition comprising a combination of two or morepropylene polymers as disclosed under “Polymer compositions” above.

In certain embodiments the polypropylene fibers are present in an amountof at least 50% by weight, preferably at least 75% by weight, morepreferably at least 85% by weight, based on the total weight of fibersin said nonwoven fabric.

The fabrics of the invention are obtainable at high production linespeeds with low occurrence of breakage. For example, the fabrics may insome embodiments be obtainable at production line speeds of at least 400m/min, preferably at least 600 m/min, preferably at least 750 m/min, forexample at 900 m/min Even at high production line speeds goodspinnability is obtained, allowing fine filaments to be formed reliablywith minimal filament breakage.

Fine Denier Fibers

Fibers of the invention may be for example continuous filament, bulkedcontinuous filament, and staple. Fibers of this invention can be usedwith advantage in the manufacture of non-wovens. Non-wovens made usingfibers of this invention have excellent properties including highstrength at low fabric base weights. Fibers of this invention are finefibers with excellent mechanical strength, allowing formation of anon-woven of low base weight which has excellent mechanical propertiesnotwithstanding the low fabric base weight. Fibers of the inventionpreferably have a dpf value of 0.3 to 5 dpf. In some embodiments thefibers may be yarns comprising a plurality of fibers with a dpf value of0.3 to 5 dpf. In other embodiments the fiber may be a monofilaments of0.3 to 5 denier. When used in nonwoven fabrics it is preferred that thefibers are monofilaments. In an illustrative method of making finedenier fibers, the polymer melt is extruded through the holes in the die(spinneret) between, 0.3 mm to 0.8 mm in diameter. Low melt viscosity ofthe polymer is important and is achieved through the use of high melttemperature (230° C. to 280° C.) and high melt flow rates (e.g. 10 g/10min to 40 g/10 min) of the polymers used. A relatively large extruder isusually equipped with a manifold to distribute a high output of moltenPP to a bank of two to fifty (alternately eight to twenty) spinnerets.Each spinhead is usually equipped with a separate gear pump to regulateoutput through that spinhead; a filter pack, supported by a “breakerplate;” and the spinneret plate within the head. The same technique maybe adapted to form yarns. The number of holes in the spinneret platedetermines the number of filaments in a yarn and varies considerablywith the different yarn constructions, but it is typically in the rangeof 50 to 250. The holes are typically grouped into round, annular, orrectangular patterns to assist in good distribution of the quench airflow.

Continuous Filament

Continuous filament yarns typically range from 40 denier to 2,000 denier(denier=number of grams/9000 meters). Filaments can range from 1 to 20denier per filament (dpf) and the range is expanding. Spinning speedsare typically 10 to 10,000 m/min (alternately 800 m/min to 1500 m/min)An exemplary method would proceed as follows. The filaments are drawn atdraw ratios of 3:1 or more (one- or two-stage draw) and wound onto apackage. Two-stage drawing allows higher draw ratios to be achieved.Winding speeds are of 2,000 m/min or more, alternately 3,500 m/min ormore are useful.

Partially Oriented Yarn (POY)

Partially oriented yarn (POY) is the fiber produced directly from fiberspinning without solid state drawing (as continuous filament mentionedabove). The orientation of the molecules in the fiber is done only inthe melt state after the molten polymer leaves the spinneret. Once thefiber is solidified, little or no drawing of the fiber takes place andthe fiber is wounded up into a package. The POY yarn (as opposed tofully oriented yarn, or FOY, which has gone through solid stateorientation and has a higher tensile strength and lower elongation)tends to have a higher elongation and lower tenacity.

Bulked Continuous Filament

Bulked Continuous Filament (“CF”) fabrication processes fall into twobasic types, one-step and two steps. For example, in a two-step process,an undrawn yarn is spun at less than 1,000 m/min (3,300 ft/min), usually750 m/min, and placed on a package. The yarn is drawn (usually in twostages) and “bulked” on a machine called a texturizer. Winding anddrawing speeds are limited by the bulking or texturizing device to 2,500m/min (8,200 ft/min) or less. A common process today is the one-stepspin/draw/text (SDT) process. It is similar to the one-step CF process,except that the bulking device is in-line. Bulk or texture changes yarnappearance, separating filaments and adding enough gentle bends andfolds to make the yarn appear fatter (bulkier).

Staple Fiber

There are two basic staple fiber fabrication processes: traditional andcompact spinning. The traditional process typically involves twosteps: 1) producing, applying finish, and winding followed by 2)drawing, a secondary finish application, crimping, and cutting intostaple. Filaments can range, for example, from 0.5 dpf to >70 dpf,(dpf=denier per filament) depending on the application. Staple lengthcan be as short as 3 mm or as long as 200 mm (0.25 in. to 8 in.) to suitthe application. For many applications the fibers are crimped. Crimpingis accomplished by over-feeding the tow into a steam-heated stuffer boxwith a pair of nip rolls. The over-feed folds the tow in the box,forming bends or crimps in the filaments. These bends are heat-set bysteam injected into the box.

Meltblown Fabrics

Meltblown fibers are fibers formed by extruding a molten thermoplasticmaterial through a plurality of fine, usually circular, die capillariesas molten threads or filaments into usually converging, usually hot andhigh velocity, gas, e.g. air, streams to attenuate the filaments ofmolten thermoplastic material to form fibers. During the meltblowingprocess, the diameter of the molten filaments is reduced by the drawingair to a desired size. Thereafter, the meltblown fibers are carried bythe high velocity gas stream and are deposited on a collecting surfaceto form a web of substantially randomly disbursed meltblown fibers. Sucha process is disclosed, for example, in U.S. Pat. No. 3,849,241 toBuntin et al., U.S. Pat. No. 4,526,733 to Lau, and U.S. Pat. No.5,160,746 to Dodge, II et al., all of which are hereby incorporatedherein by this reference. Meltblown fibers may be continuous ordiscontinuous and are generally smaller than ten microns in averagediameter.

In a conventional meltblowing process, molten polymer is provided to adie that is disposed between a pair of air plates that form a primaryair nozzle. Standard meltblown equipment includes a die tip with asingle row of capillaries along a knife edge. Typical die tips haveapproximately 30 capillary exit holes per linear inch of die width. Thedie tip is typically a 60° wedge-shaped block converging at the knifeedge at the point where the capillaries are located. The air plates inmany known meltblowing nozzles are mounted in a recessed configurationsuch that the tip of the die is set back from the primary air nozzle.However, air plates in some nozzles are mounted in a flush configurationwhere the air plate ends are in the same horizontal plane as the dietip; in other nozzles the die tip is in a protruding or “stick-out”configuration so that the tip of the die extends past the ends of theair plates. Moreover, as disclosed in U.S. Pat. No. 5,160,746 to DodgeII et al., more than one air flow stream can be provided for use in thenozzle.

In some known configurations of meltblowing nozzles, hot air is providedthrough the primary air nozzle formed on each side of the die tip. Thehot air heats the die and thus prevents the die from freezing as themolten polymer exits and cools. In this way the die is prevented frombecoming clogged with solidifying polymer. The hot air also draws, orattenuates, the melt into fibers. Other schemes for preventing freezingof the die, such as that detailed in U.S. Pat. No. 5,196,207 to Koenig,using heated gas to maintain polymer temperature in the reservoir, isalso known. Secondary, or quenching, air at temperatures above ambientis known to be provided through the die head, as in U.S. Pat. No.6,001,303 to Haynes et al. Primary hot air flow rates typically rangefrom about 20 to 24 standard cubic ft. per minute per in. of die width(SCFM/in).

Primary air pressure typically ranges from 5 to 10 pounds per squareinch gauge (psig) at a point in the die head just prior to exit. Primaryair temperature typically ranges from about 232° C. to about 315° C.,but temperatures of about 398° C. are not uncommon. The particulartemperature of the primary hot air flow will depend on the particularpolymer being drawn as well as other characteristics desired in themeltblown web.

Expressed in terms of the amount of polymer material flowing per inch ofthe die per unit of time, polymer throughput is typically 0.5 to 1.25grams per hole per minute (ghm). Thus, for a die having 30 holes perinch, polymer throughput is typically about 2 to 5 lbs/in/hr (PIH).

Moreover, in order to form meltblown fibers from an input of about fivepounds per inch per hour of the polymer melt, about one hundred poundsper inch per hour of hot air is required to draw or attenuate the meltinto discrete fibers. This drawing air must be heated to a temperatureon the order of about 204° C. to about 315° C. in order to maintainproper heat to the die tip.

Because such high temperatures must be used, a substantial amount ofheat is typically removed from the fibers in order to quench, orsolidify, the fibers leaving the die orifice. Cold gases, such as air,have been used to accelerate cooling and solidification of the meltblownfibers. In particular, in U.S. Pat. No. 5,075,068 to Milligan et al. andU.S. Pat. No. 5,080,569 to Gubernick et al., secondary air flowing in across-flow perpendicular, or 90°, direction relative to the direction offiber elongation, has been used to quench meltblown fibers and producesmaller diameter fibers. In addition, U.S. Pat. No. 5,607,701 to Allenet al. uses a cooler pressurized quench air that fills chamber 71 andresults in faster cooling and solidification of the fibers. In U.S. Pat.No. 4,112,159 to Pall, a cold air flow is used to attenuate the fiberswhen it is desired to decrease the attenuation of the fibers.

Through the control of air and die tip temperatures, air pressure, andpolymer feed rate, the diameter of the fiber formed during the meltblownprocess may be regulated. For example, typical meltblown polypropylenefibers have a diameter of 3 to 4 microns.

After cooling, the fibers are collected to form a nonwoven web. Inparticular, the fibers are collected on a forming web that comprises amoving mesh screen or belt located below the die tip. In order toprovide enough space beneath the die tip for fiber forming, attenuationand cooling, forming distances of at least about 8 to 12 inches betweenthe polymer die tip and the top of the mesh screen are required in thetypical meltblowing process.

However, forming distances as low as 4 inches are described in U.S. Pat.No. 4,526,733 to Lau (hereafter the Lau patent). As described in Example3 of the Lau patent, the shorter forming distances are achieved withattenuating air flows of at least about 37° C. cooler than thetemperature of the molten polymer. For example, the Lau patent disclosesthe use of attenuating air at about 65° C. for polypropylene melt at atemperature of about 266° C. to allow a forming distance between die tipand forming belt of 4 inches. The Lau patent incorporates passive airgaps 36 (shown in FIG. 4 of the Lau patent) to insulate the die tip.

In a preferred embodiment, melt blown fibers are produced with thepolymers described herein. In the melt blown process molten polymermoves from the extruder to the special melt blowing die. As the moltenfilaments exit the die, they are contacted by high temperature, highvelocity air (called process or primary air). This air rapidly drawsand, in combination with the quench air, solidifies the filaments. Theentire fiber forming process generally takes place within 7 mm (0.25in.) from the spinnerets. The fabric is formed by blowing the filamentsdirectly onto a forming wire, 200 mm to 400 mm (8 in. to 15 in.) fromthe spinnerets. Melt blown microfibers useful in the present inventioncan be prepared as described in Van A. Wente, “Superfine ThermoplasticFibers,” Industrial Engineering Chemistry, vol. 48, pp. 1342-1346 and inReport No. 4364 of the Naval Research Laboratories, published May 25,1954, entitled “Manufacture of Super Fine Organic Fibers” by Van A.Wente et al.

Spunbonded Fabrics

A particular embodiment of the present invention relates to spunbondedfabrics.

Conventional spunbond processes are illustrated in U.S. Pat. Nos.3,825,379; 4,813,864; 4,405,297; 4,208,366; and 4,334,340 all herebyincorporated by reference for purposes of U.S. patent practice. Thespunbonding process is one which is well known in the art of fabricproduction. Generally, continuous fibers are extruded, laid on anendless belt, and then bonded to each other, and often times to a secondlayer such as a melt blown layer, often by a heated calender roll, oraddition of a binder. An overview of spunbonding may be obtained from L.C. Wadsworth and B. C. Goswami, Nonwoven Fabrics: “Spunbonded and MeltBlown Processes” proceedings Eight Annual Nonwovens Workshop, Jul.30-Aug. 3, 1990, sponsored by TANDEC, University of Knoxville, Tenn.

A typical spunbond process consists of a continuous filament extrusion,followed by drawing, web formation by the use of some type of ejector,and bonding of the web. First, in one embodiment of the invention, aspunbonded nonwoven is obtainable from a propylene based polymer havingan MFR of 10-25 dg/min (or a propylene polymer that has been visbrokento have an MFR of 10 to 25 dg/min) in pellet form. The pelletized 10-25dg/min MFR propylene based resin is then fed into an extruder. In theextruder, the pellets simultaneously are melted and forced through thesystem by a heating melting screw. At the end of the screw, a spinningpump meters the melted polymer through a filter to a spinneret where themelted polymer is extruded under pressure through capillaries, at a rateof 0.3-1.0 grams per hole per minute. The spinneret contains a severalthousand capillaries, typically measuring 0.4-0.6 mm in diameter. Thepolymer is melted at about 30° C. to 100° C., typically 50 to 100° C.above its melting point to achieve sufficiently low melt viscosity forextrusion. The fibers exiting the spinneret are quenched and drawn intofine fibers measuring 10-40 microns in diameter by cold, high velocityair jets. The solidified fiber is laid randomly on a moving belt to forma random netlike structure known in the art as web. After web formationthe web is bonded to achieve its final strength using heated textilecalenders known in the art as thermo bond calenders. The calendersconsists of two heated steel rolls; one roll is plain and the otherbears a pattern of raised points. The web is conveyed to the calenderwherein a fabric is formed by pressing the web between the rolls at abonding temperature of about 100° C. to 200° C.

While bonding occurs within a wide temperature range the bondingtemperature must be optimized for achieving a fabric having maximummechanical strength. Over bonding, that is, bonding at a temperaturegreater than optimum results in fibers having significantly weaker fiberaround the bonding point because of excessive melting of the fiber.These become the weak points in the fabric. Under bonding, that is,bonding at a temperature lower than the optimum results in insufficientbonding at the fiber-to-fiber links. The optimum bonding temperaturedepends upon the nature of the material that the fibers are made of. Thebonding area of fabrics of the invention, as is known to those ofordinary skill in the art is dependent on the roll surfaceconfiguration, and is preferably from 10 to 30%, more preferably from 15to 30%, especially from 15 to 28%, more especially from 17 to 23%.

Annealing

Another part of the invention is that the mechanical properties referredto above can be obtained by the annealing the polymer fiber. Annealingis often combined with mechanical orientation. It is preferred to employan annealing step in the process. Annealing may also be done afterfabrication of a non-woven material from the fibers. Annealing partiallyrelieves the internal stress in the stretched fiber and restores theelastic recovery properties of the blend in the fiber. Annealing hasbeen shown to lead to significant changes in the internal organizationof the crystalline structure and the relative ordering of the amorphousand semicrystalline phases. This leads to recovery of the elasticproperties. Thermal annealing of the polymer blend is conducted bymaintaining the polymer blends or the fibers or fabrics at a temperaturebetween room temperature to a maximum of 160° C. or more preferably to amaximum of 130° C. for a period between 5 minutes to less than 7 days. Atypical annealing period is 3 days at 50° C. or 5 minutes at 100° C. Theannealing time and temperature can be adjusted for any particular blendcomposition by experimentation. While the annealing is done in theabsence of mechanical orientation, the latter can be a part of theannealing process on the fiber (past the extrusion operation) requiredto produce an elastic material. Mechanical orientation can be done bythe temporary, forced extension of the polymer fiber for a short periodof time before it is allowed to relax in the absence of the extensionalforces. Oriented polymer fibers are obtained by maintaining the polymerfibers or the articles made from a blend at an extension of 100% to 700%for a period of 0.1 seconds to 24 hours. A typical orientation is anextension of 200% for a momentary period at room temperature.

For orientation, a polymeric fiber at an elevated temperature (but belowthe crystalline melting point of the polymer) is passed from a feed rollof fiber around two rollers driven at different surface speeds andfinally to a take-up roller. The driven roller closest to the take-uproll is driven faster than the driven roller closest to the feed roll,such that the fiber is stretched between the driven rollers. Theassembly may include a roller intermediate the second roller and take-uproller to cool the fiber. The second roller and the take-up roller maybe driven at the same peripheral speeds to maintain the fiber in thestretched condition. If supplementary cooling is not used, the fiberwill cool to ambient temperature on the take up roll.

In other embodiments, the nonwoven fabrics of the present inventionrequire little to no post fabrication processing. In another embodiment,the fabrics of the present invention are annealed in a single-step by aheated roll (godet) during calendering under low tension. Depending onthe end use application, it is apparent what techniques are appropriateand what variations in process parameters are required to obtain thedesired fabric properties.

Devices and methods to convert the compositions described herein intofibers and fabrics are known in the art, see for example to EP 1340 843A1.

Useful inventive fabrics are obtainable using an apparatus for thecontinuous production of a spunbonded web of filaments, with spinneret,a cooling chamber in which the process air for cooling filaments can beinserted, a monomer exhaust device located between spinneret and coolingchamber, a stretching unit and a deposit device for depositing thefilaments to spunbonded nonwoven fabric, wherein the cooling chamber isdivided into two cooling chamber sections, wherein process air from afirst upper cooling chamber section with a volume flow VM can be pulled(such as with a vacuum) to the monomer exhaust device, said process airfrom the first upper cooling chamber section with a volume flow V1escaping into a second lower cooling chamber section and said volumeflow ratio is VM/V1 0.1 to 0.3, preferably 0.12 to 0.25.

Especially preferred volume flow ratio is from 0.15 to 0.2 VM/V1. Theflow rate is appropriately measured in m³/s. The term process air refersin particular to cooling air for filament cooling. Preferably, thefilaments are stretched aerodynamically in the stretching unit. It ispreferred that the filaments are produced as monocomponent filaments. Inprinciple also bicomponent filaments or multicomponent filaments canalso be produced.

It is preferred that process air with a volume flow V2 escapes from thesecond lower cooling chamber section and that the volume flow ratio ofthe volume flow V1 escaping from the first upper cooling chamber sectionto the volume flow V2 (V1/V2) escaping from the second lower coolingchamber section is from 0 to 0.5, preferably 0.05 to 0.5 andparticularly preferably 0.1 to 0.45. In one possible arrangement, thefilaments escaping from the second lower cooling chamber section and theprocess air escaping from second lower cooling chamber section areintroduced into the stretching unit.

It is preferred that process air from the first upper cooling chambersection is escaping with a speed v1 into the second lower coolingchamber section, that process air is escaping from the second lowercooling chamber section with a speed v2 and that the speed ratio v1/v2is 0.2 to 0.5, preferably 0.25 to 0.5 and preferentially 0.3 to 0.5. Inanother variant the speed ratio v1/v2 is from 0.35 to 0.45 and inparticular for example 0.4. Between the cooling chamber and thestretching unit an intermediate passage may be located. The intermediatechannel from the outlet of the cooling chamber to the inlet of a covertchannel of the stretching unit is converging wedge-shaped in thevertical section. Conveniently, the intermediate channel convergeswedge-shaped to the inlet of the covert channel in the vertical sectionon the entrance width of the drawing channel. In the manufacture ofcertain spunbond fabrics of the invention there is no air supplyprovided in the range of the cooling chamber and in the transitionregion between the cooling chamber and stretching unit, apart from thesupply of process air in the cooling chamber. In that regard theinvention works with a closed system. Preferably, in the section of thecooling chamber, in the region of the intermediate channel and in theregion of stretching unit no air supply from outside will be provided,apart from the supply of process air in the cooling chamber. It isrecommended that at least one diffuser should be arranged between thestretching unit and the storage device. Such a diffuser advantageouslyhas a storage device oriented toward the diverging section or a sectionwith diverging side walls. As a result a fail-safe deposition of thefilaments to non-uniform web is easier. Preferably the depositingapparatus is an endlessly circulating conveyer belt. The filaments aredeposited on this conveyer belt for spunbonded nonwoven fabric and thefabric is subsequently suitably compacted and/or consolidated,preferably the consolidation occurs in a calender.

In one suitable process for continuous production of a spunbondednonwoven fabric of the invention, the filaments are spun through aspinneret and guided past the monomer exhaust device into a coolingchamber, the filaments are cooled in the cooling chamber with processair, the cooling chamber is divided into two cooling chamber sections,and process air from a first upper cooling chamber section with a volumeflow VM can be pulled (such as with a vacuum) to the monomer exhaustdevice, said process air from the first upper cooling chamber sectionwith a volume flow V1 exiting in a second lower cooling chamber sectionand said volume flow ratio being VM/V1 0.1 to 0.3, preferably 0.12 to0.25, wherein the filaments after leaving the cooling chamber areintroduced into a stretching unit and wherein the filaments thendeposited on a conveyer belt for the spunbonded nonwoven fabric.

It is within the scope of the invention that the filaments in a nonwovenfabric of this invention are present as monocomponent filaments.

It is also within the scope of the invention that the filaments in thespunbonded fabrics of this invention are drawn. Drawing of the filamentsis carried out to obtain a filament diameter from 0.3 to 5, alternatelyfrom 0.3 to 2 denier, alternately from 0.3 to 0.9 denier. Conveniently,the filament diameter of the filaments is smaller than 3 denier,alternately small than 2.5 denier, alternately smaller than 2 denier,alternately smaller than 1 denier. The filament diameter is measured atthe spunbonded nonwoven fabric deposited filaments.

In a preferred embodiment, any of the fabrics (such as nonwoven fabrics)according to this invention have a CD specific tensile strength(determined from the peak load of the force-elongation curve as measuredby Worldwide Strategic Partners test 110.4(5) (WSP 110.4 (05)) of atleast 1 N/5 cm/gsm, preferably at least 1.1 N/5 cm/gsm, preferably atleast 1.2 N/5 cm, for a fabric basis weight in the range of 8 to 12 gsmproduced at a line speed of at least 600 m/min and more preferably atleast 700 m/min and more preferably of at least 800 m/min. CD specifictensile strength (N/5 cm/gsm) is CD strength (N/5 cm) divided by fabricbasis weight (gsm) (normalization).

In a preferred embodiment, any fabric (such as nonwoven fabric)according to this invention has a MD specific tensile strength (asmeasured by WSP 110.4 (05)) of at least 2.7 N/5 cm/gsm, preferably atleast 2.9 N/5 cm/gsm, preferably 3.0 N/5 cm/gsm, for a fabric basisweight in the range of 8 to 12 gsm produced at a line speed of at least600 m/min and more preferably at least 700 m/min and more preferably ofat least 800 m/min. MD specific tensile strength (N/5 cm/gsm) is MDstrength (N/5 cm) divided by fabric basis weight (gsm) (normalization).

In a preferred embodiment, any of the fabrics (such as nonwoven fabrics)according to this invention have a tensile strength anisotropy definedas the ratio of the specific tensile strength in the MD over the CD (asmeasured by WSP 110.4 (05)) of less than about 2.7 preferably less thanabout 2.6, preferably less than about 2.6 for a fabric basis weight inthe range of 8 to 12 gsm produced at a line speed of at least 600 m/minand more preferably at least 700 m/min and more preferably of at least800 m/min.

In a preferred embodiment, any of the inventive fabrics or other fabricscontaining fibers of this invention (such as nonwoven fabrics) have atotal hand (determined as described in the Test Methods below) of lessthan about 6.8 gr, preferably less than about 6.6 gr, preferably lessthan about 6.5 gr for a fabric basis weight in the range 8 to 12 gsmproduced at a line speed of at least 600 m/min and more preferably atleast 700 m/min and more preferably of at least 800 m/min. Preferablythe fabrics made herein have a total hand of less than about 6.8 gr andmore preferably less than about 6.5 gr.

In a preferred embodiment, any of the of the inventive fabrics or otherfabrics containing fibers of this invention (such as nonwoven fabrics)prepared according to this invention have a MD tensile modulus(determined as described in the Test Methods below) of less than about35 N/5 cm/gsm, preferably less than about 32 N/5 cm/gsm, preferably lessthan about 30 N/5 cm/gsm, for a fabric basis weight in the range of 8 to12 gsm produced at a line speed of at least 600 m/min and morepreferably at least 700 m/min and more preferably of at least 800 m/min.

In a particularly preferred embodiment, compositions which characterizethe fabrics and fibers of this invention have good spinnability (asdefined above) in combination with outstanding fiber tensile propertiesand/or fabric tensile properties when used in fabrics (e.g. CD specifictensile strength of at least 1.1 N/5 cm/gsm, a MD specific tensilestrength of at least 2.7 N/5 cm/gsm and a total hand of less than about6.8 gm force or a tensile modulus of less than about 32 N/5 cm/gsm, fora fabric basis weight in the range of 8 to 12 gsm produced at a linespeed of at least 600 m/min and more preferably at least 700 m/min andmore preferably of at least 800 m/min.

In a particularly preferred embodiment, compositions which characterizethe fabrics and fibers of this invention have good spinnability (asdefined above) in combination, when used in the inventive fabrics, witha fabric tensile anisotropy (ratio of MD over CD specific tensilestrength as determined by WSP 110.4 (05)) of less than about 2.7, for afabric basis weight in the range of 8 to 12 gsm produced at a line speedof at least 600 m/min and more preferably at least 700 m/min and morepreferably of at least 800 m/min.

In a particularly preferred embodiment, compositions which characterizethe fabrics and fibers of this invention have good spinnability (asdefined above) in combination with, when used in the inventive fabrics,outstanding fabric tensile properties (e.g. CD specific tensile strengthof at least 1.2 N/5 cm/gsm, MD specific tensile strength of at least 2.9N/5 cm/gsm, and total hand of less than about 6.6 gm force or MD tensilemodulus of less than about 30 N/5 cm/gsm, for a fabric basis weight inthe range of 8 to 12 gsm produced at a line speed of at least 600 m/minand more preferably at least 700 m/min and more preferably of at least800 m/min.

In a particularly preferred embodiment, the compositions whichcharacterize the fibers and fabrics of the invention have excellentspinnability (e.g. stable fabrication without breaks) particularly whenthin (e.g. less than 18 microns or equivalently less than about 2denier) fibers are made.

In another preferred embodiment, fabrics (such as nonwoven fabrics) madeusing the materials described herein have a: 1) A ratio of CD elongationto CD peak strength of 40 or more, when measured at speed of 100 mm/minand 200 mm gauge length (WSP110.4 (0.5)), preferably 45 or more; and

2) a CD strength of Y N/5 cm/gsm or more, where Y=−0.0005(X)+1.46(preferably 1.48, preferably 1.5, preferably 1.6), where X is theproduction line speed of the fabric is at least 400 m/min, provided theCD strength is at least 1.0 N/5 cm/gsm. CD peak elongation (alsoreferred to as CD elongation), and CD peak strength (also referred to asCD strength) are determined according to WSP 110.4 (05), using a gaugelength of 200 mm and a testing speed of 100 mm/min unless otherwiseindicated.

In an other preferred embodiment, fabrics (such as nonwoven fabrics)made using the materials described herein have a CD strength of Y N/5cm/gsm or more, where Y=−0.0009(X)+1.965 (preferably 2.1, preferably2.3), where X is the production line speed of the fabric and is at least400 m/min CD strength is determined according to WSP 110.4 (05), using agauge length of 200 mm and a testing speed of 100 mm/min.

In another preferred embodiment, fabrics (such as nonwoven fabrics) madeusing the materials described herein have a CD strength of Y N/5 cm/gsmor more, where Y=−0.0008(X)+1.85 (preferably 1.95), where X is theproduction line speed of the fabric and is at least 400 m/min. CDstrength is determined according to WSP 110.4 (05), using a gauge lengthof 200 mm and a testing speed of 100 mm/min.

In another preferred embodiment, fabrics (such as nonwoven fabrics) madeusing the materials described herein have a MD strength of Y N/5 cm/gsmor more, where Y=−0.0007(X)+2.145 (preferably 2.4), where X is theproduction line speed of the fabric and is at least 400 m/min. MDstrength (also referred to as MD peak strength) is determined accordingto WSP 110.4 (05), using a gauge length of 00 mm and a testing speed of100 mm/min.

In another preferred embodiment, fabrics (such as nonwoven fabrics) madeusing the materials described herein have a MD strength of Y N/5 cm/gsmor more, where Y=−0.0006(X)+2.34 (preferably 2.4, preferably 2.5), whereX is the production line speed of the fabric and is at least 400 m/min.MD strength (also referred to as MD peak strength) is determinedaccording to WSP 110.4 (05), using a gauge length of 200 mm and atesting speed of 100 mm/min.

In another preferred embodiment, fabrics (such as nonwoven fabrics) madeusing the materials described herein have a MD strength of Y N/5 cm/gsmor more, where Y=−0.0007(X)+2.715 (preferably 2.8, preferably 2.9),where X is the production line speed of the fabric and is at least 400m/min. MD strength (also referred to as MD peak strength) is determinedaccording to WSP 110.4 (05), using a gauge length of 200 mm and atesting speed of 100 mm/min.

In another preferred embodiment, fabrics (such as nonwoven fabrics) madeusing the materials described herein have are produced at a line speedof at least 500 m/min (preferably at least 600 m/min, at least 700m/min, at least 800 m/min, at least 850 m/min, at least 900 m/min).

INDUSTRIAL APPLICABILITY

The fibers and fabrics of the invention have wide applicability spanningseveral industries. For example, fabrics of the invention may be used inthe manufacture of hygiene products. Examples include diapers andfeminine hygiene products. The fabrics of the invention are also usefulfor medical products. Examples include medical fabric for gowns, linens,towels, bandages, instrument wraps, scrubs, masks, head wraps, anddrapes. Additionally, the fabrics of the invention are useful in themanufacture of consumer products. Examples include seat covers, domesticlinens, tablecloths, and car covers. It is also contemplated that theinventive fabrics may make-up either a portion or a component of thearticles described above.

The fibers and nonwoven webs of this invention can be formed intofabrics, garments, clothing, medical garments, surgical gowns, surgicaldrapes, diapers, training pants, sanitary napkins, panty liners,incontinent wear, bed pads, bags, packaging material, packages,swimwear, body fluid impermeable backsheets, body fluid impermeablelayers, body fluid permeable layers, body fluid permeable covers,absorbents, tissues, nonwoven composites, liners, cloth linings,scrubbing pads, face masks, respirators, air filters, vacuum bags, oiland chemical spill sorbents, thermal insulation, first aid dressings,medical wraps, fiberfill, outerwear, bed quilt stuffing, furniturepadding, filter media, scrubbing pads, wipe materials, hosiery,automotive seats, upholstered furniture, carpets, carpet backing, filtermedia, disposable wipes, diaper coverstock, gardening fabric,geomembranes, geotextiles, sacks, housewrap, vapor barriers, breathableclothing, envelops, tamper evident fabrics, protective packaging, andcoasters.

In a preferred embodiment the compositions of this invention can be usedfor disposable diaper and napkin chassis construction, including: babydiaper leg elastic, diaper frontal tape, diaper standing leg cuff,diaper chassis construction, diaper core stabilization, diaper liquidtransfer layer, diaper outer cover lamination, diaper elastic cufflamination, feminine napkin core stabilization, feminine napkin adhesivestrip. The diaper may be of various suitable shapes. For example, thediaper may have an overall rectangular shape, T-shape or anapproximately hour-glass shape. Other suitable components which may beincorporated in a diaper comprising the compositions described hereininclude waist flaps and the like which are generally known to thoseskilled in the art. Examples of diaper configurations suitable for usein connection with the instant invention which may include othercomponents suitable for use on diapers are described in U.S. Pat. No.4,798,603 to Meyer et al.; U.S. Pat. No. 5,176,668 to Bemardin; U.S.Pat. No. 5,176,672 to Bruemmer et al.; U.S. Pat. No. 5,192,606 toProxmire et al. and U.S. Pat. No. 5,509,915 to Hanson et al. each ofwhich is hereby incorporated by reference in its entirety.

Preferably, the various components of a diaper comprising the fibers andnon-wovens of this invention are assembled together employing varioustypes of suitable attachment means, such as adhesive bonding, ultrasonicbonding, thermal point bonding or combinations thereof. In the shownembodiment, for example, the topsheet and backsheet may be assembled toeach other and to the liquid retention structure with lines of adhesive,such as a hot melt, pressure-sensitive adhesive.

In another embodiment, the fibers and or non-wovens of this inventionare used in training pants. Various materials and methods forconstructing the training pants are disclosed in PCT Patent ApplicationWO 00/37009 published Jun. 29, 2000 by A. Fletcher et al; U.S. Pat. No.4,940,464 issued Jul. 10, 1990 to Van Gompel et al.; U.S. Pat. No.5,766,389 issued Jun. 16, 1998 to Brandon et al.; and U.S. Pat. No.6,645,190 issued Nov. 11, 2003 to Olson et al., which are eachincorporated herein by reference in its entirety.

In another embodiment this invention relates to fibers and fabricscomprising:

1. A propylene polymer composition comprising at least 50 mol %propylene, said polymer composition having:

a) a melt flow rate (MFR, ASTM 1238, 230° C., 2.16 kg) of about 10dg/min to about 21.5 dg/min;

b) a dimensionless Stress Ratio/Loss Tangent Index R₂ [defined by Eq.(8) below] at 190° C. from about 1.5 to about 28;

c) an onset temperature of crystallization under flow, T_(c,rheol), (asdetermined by SAOS rheology, 1° C./min as described below, where saidpolymer has 0 wt % nucleating agent present), of at least about 131° C.;and

d) an average meso run length determined by ¹³C NMR of at least about 97or higher; and

e) optionally, a loss tangent, tan δ, [defined by Eq. (2) below] at anangular frequency of 0.1 rad/s at 190° C. from about 10 to about 70.

2. The propylene polymer composition of paragraph 1 where thecomposition comprises a combination of two or more propylene polymers.

3. The propylene polymer composition of paragraph 1 or 2 where thepropylene polymer composition has a Dimensionless Stress Ratio Index R₁at 190° C. of 1.2 to 4.5.

4. The propylene polymer composition of paragraph 1, 2 or 3 where thepropylene polymer composition has a Dimensionless Shear Thinning IndexR₃ at 190° C. of 6 to 13.

5. The propylene polymer composition of paragraph 1, 2, 3 or 4 where thepropylene polymer composition has a Dimensionless LossTangent/Elasticity Index R₄ at 190° C. of 1.5 to 20.

6. The propylene polymer composition of any of paragraphs 1 to 5 wherethe propylene polymer composition has a Tmp (second melt, 1° C./min) of120° C. or more.

7. The propylene polymer composition of any of paragraphs 1 to 6 wherethe propylene polymer composition has a percent crystallinity of 20 to80%.

8. The propylene polymer composition of any of paragraphs 1 to 7 wherethe propylene polymer composition has a glass transition temperature,Tg, of −50° C. to 120° C.

9. The propylene polymer composition of any of paragraphs 1 to 8 wherethe propylene polymer composition has a crystallization temperature, Tc,(1° C./min) of 15 to 150° C.

10. The propylene polymer composition of any of paragraphs 1 to 9 wherethe propylene polymer composition has a branching index (g′_(vis)) of0.85 or more.

11. The propylene polymer composition of any of paragraphs 1 to 10 wherethe propylene polymer composition comprises a propylene polymer havingan Mw/Mn of 1 to 7, and/or an Mz/Mw of 1.5 to 2.5.

12. The propylene polymer composition of any of paragraphs 1 to 11 wherethe propylene polymer composition has a T_(c,rheol), of 135° C. or more.

13. The propylene polymer composition of any of paragraphs 1 to 12 wherethe propylene polymer composition has a T_(mp) (10° C. per minute) of120° C. or more and a T_(cp) (1° C. per minute) of 125° C. or more.

14. The propylene polymer composition of any of paragraphs 1 to 13 wherethe propylene polymer composition has a supercooling parameter SPC (1°C. per minute) of −11° C. or less and an SPC (10° C. per minute) of −1°C. or less.

15. The propylene polymer composition of any of paragraphs 1 to 14 wherethe propylene polymer composition has a T_(mp) (1° C. per minute) of140° C. or more and a dimensionless Stress Ratio Index R₁ at 190° C. of1.2 to 4.6.

16. The propylene polymer composition of any of paragraphs 1 to 15 wherethe propylene polymer composition has a T_(cp) (1° C. per minute) of125° C. or more or a T_(cp) (10° C. per minute) of 115° C. or more and aDimensionless Loss Tangent/Elasticity Index Index R₄ at 190° C. of 1.50to 20.17. A propylene polymer composition comprising a propylene polymerhaving:

-   -   1) an MFR in the range from about 10 dg/min to about 21.5        dg/min; AND    -   2) a) a Dimensionless Stress Ratio Index R₁ [defined by Eq. (7)]        at 190° C. from about 1.2 to about 4.5; OR        -   b) a Dimensionless Stress Ratio/Loss Tangent Index R₂            [defined by Eq. (8)] at 190° C. from about 1.5 to about 28;            OR        -   c) a Dimensionless Shear Thinning Index R₃ [defined by Eq.            (9)] at 190° C. from about 6 to about 13; OR        -   d) a Dimensionless Loss Tangent/Elasticity Index R₄ [defined            by Eq. (10)] at 190° C. from about 1.5 to about 20; OR    -   e) a Loss Tangent (tan δ) at an angular frequency of 0.1 rad/s        [defined by Eq. (2)] at 190° C. from about 14 to about 70; OR    -   f) a Stress Ratio (SR) at a shear rate of 500 s⁻¹ [defined by        Eq. (6)] at 190° C. from about 3.1 to about 6.1; AND    -   3) a) An onset temperature of crystallization under flow        T_(c,rheol) (via SAOS rheology, 1° C./min) with 0% nucleating        agent of at least about 131° C. or higher; OR        -   b) a T_(cp) (measured by DSC at a cooling rate of 1° C. per            minute) with 0% nucleating agent of at least about 125° C.            or higher; OR        -   c) a T_(cp) (measured by DSC at a cooling rate of 10° C. per            minute) with 0% nucleating agent of at least about 117° C.            or higher; OR        -   d) a supercooling parameter SCP (measured by DSC at a            heating and cooling rate of 10° C./min) with 0% nucleating            agent of less than about −2° C.; OR        -   e) a supercooling parameter SCP (measured by DSC at a            heating and cooling rate of 1° C./min) with 0% nucleating            agent of less than about −13° C.; AND    -   4) a) an average meso run length determined by ¹³C NMR of at        least about 97 or higher; OR        -   b) a total number of defects (stereo and regio) per 10,000            monomers of less than about 103.            18. The propylene polymer composition of paragraph 17 where            the propylene polymer has:    -   1) an MFR in the range from about 14 dg/min to about 19 dg/min;        AND    -   2) a) a Dimensionless Stress Ratio Index R₁ [defined by Eq. (7)]        at 190° C. from about 2.0 to about 3.0; OR        -   b) a Dimensionless Stress Ratio/Loss Tangent Index R₂            [defined by Eq. (8)] at 190° C. from about 2.5 to about 6.5;            OR        -   c) a Dimensionless Shear Thinning Index R₃ [defined by Eq.            (9)] at 190° C. from about 7.0 to about 10.0; OR        -   d) a Dimensionless Loss Tangent/Elasticity Index R₄ [defined            by Eq. (10)] at 190° C. from about 2.0 to about 6.0; OR        -   e) a Loss Tangent (tan δ) at an angular frequency of 0.1            rad/s [defined by Eq. (2)] at 190° C. from about 35 to about            65; OR        -   f) a Stress Ratio (SR) at a shear rate of 500 s⁻¹ [defined            by Eq. (6)] at 190° C. from about 3.3 to about 4.0; AND    -   3) a) An onset temperature of crystallization under flow        T_(c,rheol) (via SAOS rheology, 1° C./min) with 0% nucleating        agent of at least about 134° C. or higher; OR        -   b) a T_(cp) (measured by DSC at a cooling rate of 1° C. per            minute) with 0% nucleating agent of at least about 133° C.            or higher; OR        -   c) a T_(cp) (measured by DSC at a cooling rate of 10° C. per            minute) with 0% nucleating agent of at least about 123° C.            or higher; OR        -   d) a supercooling parameter SCP (measured by DSC at a            heating and cooling rate of 10° C./min) with 0% nucleating            agent of less than about −3.5° C.; OR        -   e) a supercooling parameter SCP (measured by DSC at a            heating and cooling rate of 1° C./min) with 0% nucleating            agent of less than about −17.0° C.; AND    -   4) a) an average meso run length determined by ¹³C NMR of at        least about 100 or higher; OR        -   b) a total number of defects (stereo and regio) per 10,000            monomers of less than about 100.            19. The composition of any of paragraphs 1 to 18, where            propylene polymer is has not been visbroken.            20. The composition of any of paragraphs 1 to 19, where            propylene polymer is has been visbroken.            21. The composition of any of paragraphs 1 to 20 having a 1%            secant flexural modulus of about 190 kpsi or higher.            22. The composition of any of paragraphs 1 to 21 having a            tensile strength at yield of about 4,700 psi or higher.            23. The composition of any of paragraphs 1 to 22 having a            heat distortion temperature at 66 psi of about 95° C. or            higher.            24. A blend comprising 1) a homopolypropylene having an MFR            of 22 dg/min or more (preferably 20 to 30 dg/min, preferably            22 to 28 dg/min, preferably about 25 dg/min) and 2) the            composition of any of paragraphs 1 to 23.            25. The blend of paragraph 24 wherein the homopolypropylene            having an MFR of 22 dg/min or more is present at 99 wt % to            1 wt %, based upon the weight of the blend (preferably at 95            wt % to 50 wt %, preferably at 95 wt % to 75 wt %) and the            composition of any of paragraphs 1 to 22 is present at from            1 wt % to 99 wt %, based upon the weight of the blend,            preferably 5 wt % to 50 wt %, preferably 5 wt % to 25 wt %.            26. A diaper comprising the composition or blend of any of            paragraphs 1 to 25.            Test Methods

Melt Flow Rate (MFR), defined in gr of polymer per 10 min (g/10 min orits equivalent unit dg/min), was measured according to ASTM D1238 (2.16kg, 230° C.).

Small angle oscillatory shear (SAOS) frequency sweep melt rheologyexperiments were performed at 190° C. using a 25 mm cone (1°) and plateconfiguration on a MCR301 controlled strain/stress rheometer (Anton PaarGmbH). Sample test disks (25 mm diameter, 1 mm thickness) were preparedvia compression molding of pellets (which where necessary can be madefrom fiber samples) at 190° C. using a Schwabenthan laboratory press(200T). Typical cycle for sample preparation is 1 minute withoutpressure followed by 1.5 minute under pressure (50 bars) and thencooling during 5 minutes between water cooled plates. The sample wasfirst equilibrated at 190° C. for 13 min to erase any prior thermal andcrystallization history. An angular frequency sweep was next performedfrom 500 rad/s to 0.0232 rad/s using 6 points/decade and a strain valueof 10% lying in the linear viscoelastic region determined from strainsweep experiments. All experiments were performed in a nitrogenatmosphere to minimize any degradation of the sample during rheologicaltesting.

For purposes of this invention and the claims thereto, thezero-shear-rate viscosity, η_(o), is defined from the frequencydependent storage (G′) and loss (G″) dynamic moduli and a discreterelaxation spectrum method based on a linear regression (as discussed inBird, R. B., C. F., Curtiss, R. C. Armstrong, and O. Hassager, Dynamicsof Polymeric Liquids, 2nd Ed., (Wiley, New York, 1987), Vol. 1. andDoufas, A. K., Rice, L., Thurston, W., “Shear and Extensional Rheologyof Polypropylene Melts: Experimental and Modeling Studies”, J. Rheology55, 95-126 (2011)) as follows:

$\begin{matrix}{\eta_{o} = {\sum\limits_{j = 1}^{M}{\lambda_{j}G_{j}}}} & (1)\end{matrix}$where M is the number of discrete relaxation modes that depends on therange of experimental angular frequencies as outlined in Bird et al.(1987), λ_(j) is a discrete relaxation time of the discrete spectrum andG_(j) is the corresponding shear modulus.

In case of compositions where the terminal zone (i.e., G′ proportionalto w and G″ proportional to ω has not been reached within the frequencyrange of the experiment thus the complex viscosity |η*| not reaching aplateau value, η_(o) should be measured via melt creep experiments asdiscussed in Macosko (C. W., Rheology Principles, Measurements andApplications (Wiley-VCH, New York, 1994) and Ansari et al. (Ansari, M.,S. Hatzikiriakos, A. Sukhadia, D. Rohlfing, “Rheology of Ziegler-Nattaand Metallocene High-Density Polyethylenes: Broad Molecular WeightDistribution Effects”, Rheol. Acta 50, 17-27, 2011) In all the examplespresented in this invention, Eq. (1) for determination of thezero-shear-rate viscosity η_(o) was used. From the storage (G′) and loss(G″) dynamic moduli [Macosko, C. W., Rheology Principles, Measurementsand Applications (Wiley-VCH, New York, 1994)], the loss tangent (tan δ)is defined as:

$\begin{matrix}{{\tan\;\delta} = \frac{G^{''}}{G^{\prime}}} & (2)\end{matrix}$The loss tangent, tan δ, especially at low angular frequencies (e.g. 0.1rad/s), is a measure of melt elasticity and relates to the molecularcharacteristics (e.g. distribution of short and long chains, density ofmolecular entanglements, chain branching etc.) of the composition. Inthe current invention, the first normal stress difference (Ni) at asteady shear flow of constant shear rate {dot over (γ)} is determined asa function of the dynamic moduli, G′ and G″, as follows [Laun, H. M.,“Prediction of elastic strains of polymer melts in shear andelongation,” J. Rheol. 30 459-501 (1986)]:

$\begin{matrix}{{N_{1}\left( \overset{\bullet}{\gamma} \right)} = {{2{G^{/}\left\lbrack {1 + \left( \frac{G^{/}}{G^{//}} \right)^{2}} \right\rbrack}^{0.7}\mspace{14mu}{for}\mspace{14mu}\omega} = \overset{\bullet}{\gamma}}} & (3)\end{matrix}$where G′ and G″ refer to an angular frequency ω and the temperature ofboth SAOS and steady shear experiments is identical, N. Eq. (3) isreferred to here as “Laun rule”. In the present invention, the steadyshear stress τ_(yx) is calculated from the norm of the complex viscosity|η*| according to the Cox-Merz rule [Cox, W. P. and E. H. Merz,“Correlation of dynamic and steady flow viscosities,” J. Polym. Sci. 28,619-621 (1958)]:

$\begin{matrix}{{\tau_{yx}\left( \overset{\bullet}{\gamma} \right)} = {{\omega{{\eta^{*}(\omega)}}\mspace{14mu}{for}\mspace{14mu}\omega} = \overset{\bullet}{\gamma}}} & (4)\end{matrix}$where the norm of the complex viscosity is calculated from G′ and G″ asa function of frequency ω as follows [Macosko, C. W., RheologyPrinciples, Measurements and Applications (Wiley-VCH, New York, 1994)]:

$\begin{matrix}{{{\eta^{*}(\omega)}}\mspace{11mu} = \frac{\left( {G^{\prime 2} + G^{''2}} \right)^{1/2}}{\omega}} & (5)\end{matrix}$The stress ratio (SR) is defined as follows:

$\begin{matrix}{{{SR}\left( \overset{\bullet}{\gamma} \right)} = \frac{N_{1}\left( \overset{\bullet}{\gamma} \right)}{\tau_{yx}\left( \overset{\bullet}{\gamma} \right)}} & (6)\end{matrix}$Applicability of both Cox-Merz [Cox and Merz (1957)] and Laun [Laun1986)] rules was demonstrated for a variety of polypropylene systems inShear and Extensional Rheology of Polypropylene Melts: Experimental andModeling Studies, Doufas et al., J. Rheol. 55, 95 (2011). Based on theabove rheological properties, several rheological indexes are definedrelated to the molecular characteristics of the composition as follows:Dimensionless Stress Ratio Index R₁:R ₁=(SR(500 s⁻¹)η_(o))/2040  (7)where η_(o) [Eq. (1)] is in units of Pa s.Dimensionless Stress Ratio/Loss Tangent Index R₂:

$\begin{matrix}{R_{2} = {\left( \frac{{{SR}\left( {500\mspace{14mu} s^{- 1}} \right)}\eta_{o}}{\tan\;{\delta\left( {0.1\mspace{14mu}{rad}\text{/}s} \right)}} \right)/248}} & (8)\end{matrix}$where η_(o) [Eq. (1)] is in Pa s.Dimensionless Shear Thinning Index R₃

$\begin{matrix}{R_{3} = \frac{\eta_{o}}{\eta\left( {500\mspace{14mu} s^{- 1}} \right)}} & (9)\end{matrix}$where the steady shear viscosity η(500 s⁻¹) is calculated from Eq. (5)and use of the Cox-Merz rule [Cox, W. P. and E. H. Merz, “Correlation ofdynamic and steady flow viscosities,” J. Polym. Sci. 28, 619-621(1958)]. Dimensionless Loss Tangent/Elasticity Index R ₄

$\begin{matrix}{R_{4} = {\frac{\eta_{o}}{\tan\;{\delta\left( {0.1\mspace{14mu}{rad}\text{/}s} \right)}}/8.55}} & (10)\end{matrix}$where η_(o) [Eq. (1)] is in units of Pa s.As mentioned, the loss tangent, tan δ, at low angular frequency (e.g.0.1 rad/s) is sensitive to the molecular structure and relates to themelt longest relaxation time as well as creep related properties (e.g.steady state creep compliance and recoverable creep compliance) (C. W.Macosko, Rheology Principles, Measurements and Applications (Wiley-VCH,New York, 1994). Therefore, the rheological indexes intrinsic to thecomposition, e.g. those defined in Equations (7)-(8), (10), can be inprinciple expressed in terms of the longest relaxation time and meltcreep properties.Crystallization Via SAOS Rheology:

Crystallization was monitored via SAOS rheology, where the sample wascooled down from the molten state (at 190° C.) at a fixed cooling rateusing a 25 mm parallel plate configuration on an ARES 2001 (TAInstruments) controlled strain rheometer. Sample test disks (25 mmdiameter, 2.5 mm thickness) were made with a Carver Laboratory press at190° C. Samples were allowed to sit without pressure for approximately 3minutes in order to melt and then held under pressure for three minutesto compression mold the sample. The disks were originally approximately2.5 mm thick, however after sample trimming off the parallel plates, agap of 1.9 mm between the plates was used. Thermal expansion of thetools was taken into account during SAOS testing to maintain a constantgap throughout the test. The sample was first heated from roomtemperature to 190° C. The sample was equilibrated at 190° C. (moltenstate) for 15 min to erase any prior thermal and crystallizationhistory. The temperature was controlled reproducibly within ±0.5° C. Thesample was then cooled from 190° C. at a constant cooling rate of 1°C./min and an angular frequency of 1 rad/s using a strain of 1% lying inthe linear viscoelastic region. For termination of the experiment, amaximum torque criterion was used. Upon the onset of crystallizationduring the rheological test, the instrument goes into an overloadcondition when maximum torque is reached and the test is stoppedautomatically. All experiments were performed in a nitrogen atmosphereto minimize any degradation of the sample during rheological testing.Crystallization was observed by a steep/sudden increase of the complexviscosity and a steep/sudden (step-like) decrease of the loss tangenttan δ (i.e., a plot of complex viscosity vs. temperature and losstangent vs. temperature depict a neck-like region of sudden change inthe rheological properties due to occurrence of crystallization). The“onset crystallization temperature via rheology”, T_(c,rheol), isdefined as the temperature at which a steep (i.e., neck-like) increaseof the complex viscosity and a simultaneous steep decrease of tan δ isobserved. The reproducibility of T_(c,rheol) is within ±1° C. Thereproducibility of the complex modulus and dynamic moduli as a functionof temperature is within 3%.

Differential Scanning Calorimetry (DSC)

Peak crystallization temperature (T_(cp)), peak melting temperature(T_(mp)) and heat of fusion (ΔH_(f)) were measured via DifferentialScanning calorimetry (DSC) on pellet samples using a DSCQ200 (TAInstruments) unit. The DSC was calibrated for temperature using fourstandards (tin, indium, cyclohexane and water). The heat flow of indium(28.46 J/g) was used to calibrate the heat flow signal. A sample of 3 to5 mg of polymer, typically in pellet form, was sealed in a standardaluminum pan with flat lids and loaded into the instrument at roomtemperature.

In the case of determination of T_(cp) and T_(mp) corresponding to 1°C./min cooling and heating rates, the following procedure was used. Thesample was first equilibrated at 25° C. and subsequently heated to 200°C. using a heating rate of 20° C./min (first heat). The sample was heldat 200° C. for 5 min to erase any prior thermal and crystallizationhistory. The sample was subsequently cooled down to 95° C. with aconstant cooling rate of 1° C./min (first cool). The sample was heldisothermal at 95° C. for 5 min before being heated to 200° C. at aconstant heating rate of 1° C./min (second heat). The exothermic peak ofcrystallization (first cool) was analyzed using the TA UniversalAnalysis software and the peak crystallization temperature (T_(cp))corresponding to 1° C./min cooling rate was determined. The endothermicpeak of melting (second heat) was also analyzed using the TA UniversalAnalysis software and the peak melting temperature (T_(mp))corresponding to 1° C./min cooling rate was determined.

In the case of determination of T_(cp) and T_(mp) corresponding to 10°C./min cooling and heating rates, the following procedure was used. Thesample was first equilibrated at 25° C. and subsequently heated to 200°C. using a heating rate of 10° C./min (first heat). The sample was heldat 200° C. for 10 min to erase any prior thermal and crystallizationhistory. The sample was subsequently cooled down to 25° C. with aconstant cooling rate of 10° C./min (first cool). The sample was heldisothermal at 25° C. for 10 min before being heated to 200° C. at aconstant heating rate of 10° C./min (second heat). The exothermic peakof crystallization (first cool) was analyzed using the TA UniversalAnalysis software and the peak crystallization temperature (T_(cp))corresponding to 10° C./min cooling rate was determined. The endothermicpeak of melting (second heat) was also analyzed using the TA UniversalAnalysis software and the peak melting temperature (T_(mp))corresponding to 10° C./min heating rate was determined.

In either method of determining crystallization and melting peaktemperatures, the same cooling and heating rate (1° C./min or 10°C./min) was always kept during the second (cool) and third (heat)cycles, respectively. For example, in cases where T_(mp) is listed withits associated heating rate, it is implied that the cooling rate of thepreceding cycle was at the same rate as the heating cycle. The percentcrystallinity (X %) is calculated using the formula: [area under the DSCcurve (in J/g)/H^(o) (in J/g)]*100, where the area under the DSC curverefers here to the first cool cycle and H^(o) is the heat of fusion forthe homopolymer of the major monomer component. These values for H^(o)are to be obtained from the Polymer Handbook, Fourth Edition, publishedby John Wiley and Sons, New York 1999, except that a value of 290 J/g isused as the equilibrium heat of fusion (H^(o)) for 100% crystallinepolyethylene, a value of 140 J/g is used as the equilibrium heat offusion (H^(o)) for 100% crystalline polybutene, and a value of 207J/g)(H^(o)) is used as the heat of fusion for a 100% crystallinepolypropylene.

In the present invention, the difference between the melting andcrystallization peak temperatures (T_(mp)−T_(cp)) as measured by DSC(either at 1° C./min or 10° C./min temperature ramp rates) is referredto as “the supercooling range” and is expressed in ° C. The“supercooling limit”, SCL, is defined according to U.S. Pat. No.7,807,769 and US 2010/0113718 as follows:SCL=0.907T _(mp)−99.64  (11)where T_(mp) and SCL are expressed in ° C. U.S. Pat. No. 7,807,769 andUS Patent Application Publication No. 2010/0113718 define SCL withT_(mp) corresponding to a heating rate of 10° C./min (second heat),however in the present invention Eq. (11) is also used to define SCL ata heating rate of 1° C./min (second heat). The following parameterreferred to as “supercooling parameter” SCP is defined here as follows:SCP=T _(mp) −T _(cp)−SCL  (12)where all parameters on the right hand side of Eq. (12) are expressed in° C. and refer to either a temperature ramp rate of 1° C./min or 10°C./min as indicated. In Eq. (12), SCL is calculated from Eq. (11).Molecular Weights (Mw, Mn, Mz and Mv) by Gel-Permeation Chromatography(GPC)

Molecular weight distributions were characterized using Gel-PermeationChromatography (GPC), also referred to as Size-Exclusion Chromatography(SEC). Molecular weights (weight average molecular weight M_(w), numberaverage molecular weight M_(n), Z average molecular weight M_(z) andviscosity average molecular weight M_(v)) were determined usingHigh-Temperature Gel-Permeation Chromatography equipped with adifferential refractive index detector (DRI). Experimental details onthe measurement procedure are described in the literature by T. Sun, P.Brant, R. R. Chance and W. W. Graessley, Macromolecules, Volume 34,Number 19, 6812-6820 (2001) and in U.S. Pat. No. 7,807,769.

A Polymer Laboratories PL-GPC-220 high temperature SEC system withtriple detection and three Polymer Laboratories PLgel 10 micron Mixed Bcolumns was used. The three detectors in series are: Wyatt DAWN “EOS”MALLS 18 angle laser light scattering detector first, followed by theDRI detector and finally by the Differential Viscometer detector. Thedetector output signals are collected on Wyatt's ASTRA software andanalyzed using a GPC analysis program. The detailed GPC conditions arelisted in the Table 8 of U.S. Pat. No. 7,807,769. A theoretical basisfor the data analysis can be also found in U.S. Pat. No. 7,807,769.

A nominal flow rate of 0.5 cm³/min, and a nominal injection volume of300 mL were used. The various transfer lines, columns and differentialrefractometer (the DRI detector, used mainly to determine elutionsolution concentrations) are contained in an oven at 145° C.

Standards and samples were prepared in inhibited TCB(1,2,4-trichlorobenzene) solvent. Four NBS polyethylene (PE) standardswere used for calibrating the GPC. The PE standards were NIST 1482a,NIST 1483a; NIST1484a (narrow PE standards) and NIST 1475a (broad PEstandards). The samples were accurately weighted and diluted to a ˜1.5mg/mL concentration and recorded. The standards and samples were placedon a PL Labs 260 Heater/Shaker at 160° C. for two hours. These werefiltered through a 2.0 micron steel filter cup and then analyzed.

The branching index (g′_(vis)) is calculated using the output of theSEC-DRI-LS-VIS method (described on page 37 of U.S. Pat. No. 7,807,769for g′) as follows. The average intrinsic viscosity, [η]_(avg), of thesample is calculated by:

$\begin{matrix}{\lbrack\eta\rbrack_{avg} = \frac{\sum{c_{i}\lbrack\eta\rbrack}_{i}}{\sum c_{i}}} & (13)\end{matrix}$where the summations are over the chromatographic slices, i, between theintegration limits. The branching index g′_(vis) is defined as:

$\begin{matrix}{g_{vis}^{\prime} = \frac{\lbrack\eta\rbrack_{avg}}{{kM}_{v}^{\alpha}}} & (14)\end{matrix}$where, for purpose of this invention and claims thereto, α=0.695 andk=0.000579 for linear ethylene polymers, α=0.705 and k=0.0002288 forlinear propylene polymers, and α=0.695 and k=0.000179 for linear butenepolymers. The denominator of Eq. (12) represents the calculatedtheoretical intrinsic viscosity of a linear polymer. M_(v) is theviscosity-average molecular weight based on molecular weights determinedby LS analysis.Tacticity Determination by ¹³C NMR

Carbon NMR spectroscopy was used to measure meso pentads, stereo andregio defect concentrations in the polypropylene. Carbon NMR spectrawere acquired with a 10-mm broadband probe on a Varian spectrometerhaving a ¹³C frequency of at least 100 MHz. The samples were prepared in1,1,2,2-tetrachloroethane-d2 (TCE). Sample preparation (polymerdissolution) was performed at 140° C. where 0.25 grams of polymer wasdissolved in an appropriate amount of solvent to give a final polymersolution of 3 ml. In order to optimize chemical shift resolution, thesamples were prepared without chromium acetylacetonate relaxation agent.

Chemical shift assignments for the stereo defects (given as stereopentads) can be found in the literature [L. Resconi, L. Cavallo, A.Fait, and F. Piemontesi, Chem. Rev. 2000, 100, pages 1253-1345]. Thestereo pentads (e.g. mmmm, mmmr, mrm, etc.) can be summed appropriatelyto give a stereo triad distribution (mm, mr and rr) and the molepercentage diads (m and r). Three types of regio defects werequantified: 2,1-erythro, 2,1-threo and 3,1-insertion. The structures andpeak assignments for these are also given in the reference by Resconi etal. The concentrations for all regio defects (punctuations) are given interms of number of regio defects per 10,000 monomer units (D_(R)).Accordingly, the concentration of stereo defects (punctuations) is givenas the number of stereo defects per 10,000 monomer units (Ds). The totalnumber of defects per 10,000 monomers (D_(total)) is calculated as:D _(total) =D _(S) +D _(R)  (15)The average meso run length (MRL) represents the total number ofpropylene units (on the average) between defects (stereo and regio)based on 10,000 propylene monomers and is calculated as follows:

$\begin{matrix}{{M\; R\; L} = \frac{10,000}{D_{total}}} & (16)\end{matrix}$The definition of MRL in this invention [Eq. (16)] is based upon thenumber of structural chain punctuations or defects that result frompropylene insertions that have occurred in a non-regular fashion (stereoand regio defects). It does not include the punctuations due to thepresence of comonomer (e.g. ethylene in a polypropylene randomcopolymer). The regio defects each give rise to multiple peaks in thecarbon NMR spectrum, and these are all integrated and averaged (to theextent that they are resolved from the other peaks in the spectrum), toimprove the measurement accuracy. The chemical shift offsets of theresolvable resonances used in the analysis are tabulated in U.S. Pat.No. 7,807,769. The average integral for each defect is divided by theintegral for one of the main propylene signals (CH3, CH, CH2) andmultiplied by 10,000 to determine the defect concentration per 10,000monomers.Bulk Physical Properties Measurements

The flexural modulus (1% secant flexural modulus) is measured accordingto ASTM D790A, using a crosshead speed of 1.27 mm/min (0.05 in/min) anda support span of 50.8 mm (2.0 in) using an Instron machine.

The tensile properties such as tensile strength at yield (also referredto here as yield stress) and elongation at yield (also referred to hereas yield strain) were measured as per ASTM D638, with a crosshead speedof 50.8 mm/min (2.0 in/min) and a gauge length of 50.8 mm (2.0 in),using an Instron machine.

Heat distortion temperature (HDT) is measured according to ASTM D648using a load of 0.45 MPa (66 psi) or 1.8 MPa (264 psi) as designated.

POY Fiber Testing

The total denier of the POY fibers expressed in grams per 9000 m of yarnis measured by determining the weight of 90 m of yarn which are windedoff the fiber core using an Alfred Suter Co. denier wheel. An averagedenier per filament (dpf) is defined as the measured denier of the yarnover the number of filaments (72). Excellent agreement was found betweenthe measured dpf and that calculated from the mass throughput per holeand take-up speed as follows:

$\begin{matrix}{{dpf} = \frac{9000\mspace{14mu} W}{u_{L}}} & (17)\end{matrix}$Tensile testing of POY fibers was performed with a Textechno Statimat™unit which is a microprocessor based machine that tests the strength andelongation of yarns and fibers. The instrument used was specificallyStatimat M, S/N 23523, CRE type equipped with software FPAM 0210E usinga Microsoft operating system. For all tests, the gauge length was 100 mmand the stretching speed was 1270 mm/min.Nonwoven Fabric Testing

Fabric basis weight defined as the mass of fabric per unit area wasmeasured by weighing 3 12″×12″ fabric pieces and reporting an averagevalue expressed in g/m² (gsm).

The fiber thickness is expressed as “denier” or equivalently as “denierper filament” (dpf) and is the weight in grams per 9000 meters of fiberas is commonly known in the art. The fiber diameter and dpf were relatedin this invention according to the following equation based on thedefinition and the mass balance of the spinning process:

$\begin{matrix}{d = \sqrt{\frac{141471\mspace{11mu}{dpf}}{\rho}}} & (18)\end{matrix}$where d is the diameter of a single fiber in units of microns and is thefiber density (taken in this invention as 900 kg/m³ for polypropylene).

Fibers were isolated and their diameter (thickness) was measured usingthe following method: A portion of spunbonded fibers (taken from thebelt before entering the thermal bonding step) was carefully cut from alarger sample using a fresh double-edge razor blade and a small portionof the fiber sample was isolated for thickness measurement. Special carewas taken to avoid elongation or deformation of fibers when handling.Fibers were mounted between a slide and coverslip in an immersion fluidand examined using the polarizing light microscope (Olympus BX50)equipped with a rotating stage, crossed polars, 20× objective lens, anddigital camera (Optronics) driven by Media Cybernetics ImagePro imageprocessing software. Fibers were examined under the followingconditions: 90° crossed polars; condenser aperture fully open (tominimize diffraction effects that increase the apparent thickness of thefibers); fibers rotated to angle of maximum brightness. Digital imagesof 15 fibers were acquired and calibrated. Fiber diameters were measuredto the nearest micrometer using Media Cybernetics ImagePro imageprocessing software. Fiber denier was subsequently calculated from theaverage measured fiber diameter d via Eq. (18).

Tensile properties of nonwoven fabrics such as tensile strength and %elongation in both machine (MD) and cross (CD) directions were measuredaccording to standard method WSP 110.4 (05) with a gauge length of 200mm and a testing speed of 100 mm/min, unless otherwise indicated. Thewidth of the fabric specimen was 5 cm. For the tensile testing, anInstron machine was used (Model 5565) equipped with Instron Bluehill 2(version 2.5) software for the data analysis. From the force-elongationtensile curves, the software reports a tensile modulus value (units N/5cm/gsm) in both MD and CD directions which is calculated according tothe following algorithm:

1. search the data from the first data point to the maximum load value

2. use the first data point and maximum load point as the start and endvalues respectively.

3. divide the data between the start and end values into 6 equal regionswith 0% overlap.

4. apply a least square fit algorithm to all of the points in eachregion to determine the slope of each region.

5. determine the pair of consecutive regions that has the highest slopesum.

6. from this pair, determine which region has the highest slope andassigns the reported modulus value to that region.

A lower the value of tensile modulus is indicative of a less stiff andsofter fabric.

Softness or “hand” as it is known in the art is measured using theThwing-Albert Instruments Co. Handle-O-Meter (Model 211-10-B/AERGLA).The quality of “hand” is considered to be the combination of resistancedue to the surface friction and flexibility of a fabric material. TheHandle-O-Meter measures the above two factors using an LVDT (LinearVariable Differential Transformer) to detect the resistance that a bladeencounters when forcing a specimen of material into a slot of paralleledges. A 3½ digit digital voltmeter (DVM) indicates the resistancedirectly in gram force. The “total hand” of a given fabric is defined asthe average of 8 readings taken on two fabric specimens (4 readings perspecimen). For each test specimen (5 mm slot width), the hand ismeasured on both sides and both directions (MD and CD) and is recordedin grams. A decrease in “total hand” indicates the improvement of fabricsoftness.

The Elmendorf tear strength (expressed in gr/gsm) of nonwoven fabricswas measured in both MD and CD directions with an Elmendorf tear machine(Thwing Albert Instrument Company) according to ASTM D 1922.

CD peak elongation (also referred to as CD elongation), and CD peakstrength (also referred to as CD strength) are determined according toWSP 110.4 (05), using a gauge length of 200 mm and a testing speed of100 mm/min MD peak elongation (also referred to as MD elongation), andMD peak strength (also referred to as MD strength) are determinedaccording to WSP 110.4 (05), using a gauge length of 200 mm and atesting speed of 100 mm/min.

Unless otherwise noted, all fabric tests described above were performedat least 20 days from the day of fabric manufacturing to ensureequilibration of properties and account for any effects that may alterthe fabric properties over time. Unless otherwise noted, all fabrictests described above were performed at least 20 days from the day offabric manufacturing to ensure equilibration of properties and accountfor any effects that may alter the fabric properties over time. Fabrictensile properties measurements herein are unless the contrary isindicated measured using fabrics which have a bonding area of about 18%with about 50 bonding crossing points per cm². Fabric tensile propertiesare preferably measured using fabrics that have been calendered at anoptimum calendering temperature, defined as a temperature giving themaximum CD tensile strength. Optimum calendering temperatures for thefabrics of the invention are typically in the range of from about 145°C. to about 160° C. Where, as in certain embodiments describedhereinafter, calendering is carried out using calender rollsincorporating oil as heating medium, a heating medium temperature willtypically need to be selected in order to achieve the desiredcalendering temperature.

EXAMPLES

A number of controlled rheology propylene polymers were explored, wherea base PP resin with MFR of approx. 0.5 to 5 dg/min and preferably fromabout 0.8 to about 3 dg/min was peroxide cracked (controlled-rheologypropylene polymers) in an extruder to obtain a final MFR in the range of10 to 25 dg/min. It was surprisingly found that resins with a certainrange of the key melt rheological, crystallization and tacticityparameters described below exhibited the unexpected combination ofexcellent spinnability and high fiber/fabric strength even at low basisweight fabrics (e.g. <15 g/m²).

Materials

A propylene polymer PP-1 was treated according to the peroxidevisbreaking procedure described below to obtain the compositions ofExamples 1 to 8. PP-1 is reactor grade Ziegler-Natta propylenehomopolymer in pellet form having a MFR of 2 dg/min, M_(w)/M_(n) ofabout 4.3 and a T_(mp) (10° C./min) of 164.3° C. PP-1 contains anadditive package typical of that used in spunmelt nonwoven applicationse.g. as disclosed in WO2010/087921.

The composition of Example 9 is an extruder (physical) blend of twopropylene polymers: A and B in weight ratio of 60/40. Polymer A with anMFR of about 13 dg/min was obtained in pellet form from peroxidevisbreaking treatment of propylene polymer PP-2 according to theprocedure described below. PP-2 is a reactor grade Ziegler-Nattapropylene homopolymer having a MFR of 4.5 dg/min, M_(w)/M_(n) of about4.7 and a T_(mp) (10° C./min) of about 165° C. Polymer B having an MFRof about 40 dg/min was obtained in pellet form from peroxide visbreakingtreatment of propylene polymer PP-3 according to the procedure describedbelow. PP-3 is a reactor grade Ziegler-Natta propylene-ethylene randomcopolymer of about 2.75% by weight in ethylene with an MFR of about 1.7dg/min After extruder blending of pelletized polymers A and B in aweight ratio of 60/40, the polymer of example 9 was obtained with an MFRof 23.5 dg/min and an ethylene content of about 1.3% by weight.

Inventive example 20 is a blend of a controlled rheologyhomo-polypropylene available from ExxonMobil Chemical Company, HoustonTex. under the Tradename PP3155 and propylene polymer PP1 (both inpellet form) in a weight ratio of about 70/30 compounded on a 92 mm twinscrew extruder.

Inventive example 21 is a blend of a controlled rheologyhomo-polypropylene available from ExxonMobil Chemical Company, HoustonTex. under the Tradename PP3155 (MFR of 35 dg/min) and propylene polymerPP1 (both in pellet form) in a weight ratio of 70/30, compounded on a 30mm twin screw extruder.

Inventive example 22 is a controlled rheology (visbroken) propylenepolymer whose base polymer is a blend of a homo-polypropylene availablefrom ExxonMobil Chemical Company, Houston Tex. under the TradenamePP5341E1 (MFR of 0.8 dg/min) and propylene polymer PP1 (both in pelletform) in a weight ratio of 25/75. The base polymer (blend) was treatedaccording to the peroxide visbreaking procedure on a 30 mm twin screwextruder to obtain the inventive compositions of example 22.

Examples 1 to 9 and 21 are Examples illustrating an especially preferredembodiment of the invention. Examples 14 to 20, 22 and 23 hereinillustrate a further embodiment of the invention. Reference Examples 10to 13 relate to polymer compositions outside the scope of the presentinvention.

Example 23 is a controlled rheology (visbroken) propylene polymer whosepolymer is a reactor grade homopolymer polypropylene available fromExxonMobil Chemical Company, Houston Tex. under the Tradename PP5341E1(MFR of 0.8 dg/min) in pellet form. The base polymer was treatedaccording to the peroxide visbreaking procedure on a 30 mm twin screwextruder to obtain the inventive compositions of example 23.

Reference examples 10-12 relate to Ziegler-Natta controlled-rheologypropylene homopolymers having a MFR of 36-39 dg/min and a T_(mp) (10°C./min) of about 163° C. available from ExxonMobil Chemical Company,Houston Tex. under the Tradename PP 3155E3.

Reference example 13 relates to metallocene reactor grade propylenehomopolymer having a MFR of 24 dg/min and a T_(mp) (10° C./min) of152.5° C. available from ExxonMobil Chemical Company, Houston Tex. underthe Tradename Achieve™ 3854.

Examples 14 and 15 represent metallocene propylene homopolymer having amelt flow index (230° C., 2.16 kg ISO 1133) of 15 about dg/min and a Tmof about 153° C. available from Total Petrochemicals, Feluy Belgiumunder the Trade name Lumicene™ MR 2002.

Examples 16 and 17 represent Ziegler-Natta controlled-rheology propylenehomopolymer having an MFR of about 18 dg/min and a T_(mp) (10° C./min)of about 165° C. available from Borealis Group, Port Murray N.J. underthe Trade name HF420FB.

Example 18 is a Ziegler-Natta controlled rheology propylene homopolymerhaving an MFR of 13.5 dg/min and a T_(mp) (10° C./min) of 163.7° C.available from Lyondell Basell, Houston, Tex. under the trade nameMoplen™ HP552N.

Example 19 is a Ziegler-Natta controlled rheology propylene homopolymerhaving an MFR of 17 dg/min and a T_(mp) (10° C./min) of 164.7° C.available from Lyondell Basell, Houston, Tex. under the trade nameMoplen™ PP567P.

Visbreaking Procedure

The starting propylene polymers were peroxide visbroken (cracked) on a92 mm twin screw extruder (ZSK 92, Werner Pfleiderer) at a productionrate of 3,000 lbs/hr and a screw speed of 440 rpm. A peroxide level of200 to 500 ppm Lupersol™ 101(2,5-bis(tert-butylperoxy)-2,5-dimethylhexane) was used to crack thestarting polymers (inventive Examples 1-9) to a higher MFR (see table1). The starting propylene polymers are described under “Materials”above. The extruder had two feeders, one for polymer and one for theperoxide visbreaking agent. The set temperature of the extruder zonesand the die was in the range of 190° C. to 220° C., while the melttemperature was in the range of 200° C. to 215° C. depending on thestarting propylene polymer and targeted final MFR. A standard 100 meshwire (150 microns nominal porosity) was used for all extruder runs. Ineach Example, pellets were produced with a density in the range of 40 to50 ppg (pellets per gram) using an underwater pelletizer. The pelletscan be used to form fibers or fabrics.

The polymer properties of the inventive and reference compositions arereported in Tables 1-7 below:

TABLE 1 List of polymer compositions. Reactor (R) or Controlled RheologyFinal Composition Example (CR) MFR (dg/min) 1 CR 16.5 2 CR 17.0 3 CR17.0 4 CR 17.0 5 CR 16.7 6 CR 13.0 7 CR 14.2 8 CR 19.0 9 CR 23.5 10 CR35.0 11 CR 39.0 12 CR 37.0 13 R 24.0 14 R 15.8 15 R 14.4 16 CR 17.7 17CR 18.6 18 CR 13.5 19 CR 17.0 20 CR (Blend) 16.7 21 CR (Blend) 15.6 22CR (Blend) 15.3 23 CR 16.1

TABLE 2 Rheological properties of polymer compositions includingrheology indexes and onset crystallization temperature under flowdetermined via SAOS rheology. η_(o) tanδ@ SR @ Rheology RheologyRheology Rheology T_(c, rheol) Example (Pa · s) 0.1 rad/s 500 s⁻¹ IndexR₁ Index R₂ Index R₃ Index R₄ (° C.) 1 1362.1 47.1 3.68 2.5 4.3 8.2 3.4140.0 2 1422.4 41.3 3.68 2.6 5.1 8.3 4.0 140.0 3 1293.1 56.2 3.67 2.33.4 8.1 2.7 137.0 4 1469.8 50.1 3.74 2.7 4.4 8.3 3.4 140.0 5 1435.5 49.13.68 2.6 4.3 8.1 3.4 132.0 6 1737.1 34.9 3.95 3.4 7.9 9.6 5.8 138.0 71612.1 42.3 3.86 3.0 5.9 9.1 4.5 132.0 8 1211.2 63.1 3.49 2.1 2.7 7.32.2 132.0 9 1090.5 45.5 3.31 1.8 3.2 7.5 2.8 136.0 10 702.6 82.1 2.901.0 1.0 5.6 1.0 128.0 11 706.9 71.1 2.88 1.0 1.2 5.6 1.2 130.0 12 694.087.4 2.90 1.0 0.9 5.8 0.9 136.5 13 952.6 161.3 3.30 1.5 0.8 5.1 0.7124.0 14 1284.5 58.2 3.63 2.3 3.2 6.9 2.6 125.0 15 1404.5 63.1 4.39 3.03.9 6.1 2.6 124.5 16 1392.2 52.6 3.54 2.4 3.8 7.7 3.1 126.0 17 1223.953.8 4.38 2.6 4.0 6.5 2.7 129.0 18 2319.0 12.6 4.03 4.6 29.9 14.5 21.5130.0 19 1456.9 48.9 3.70 2.6 4.4 8.3 3.5 128.5 20 1941.1 14.3 4.87 4.626.7 10.6 15.9 132.0 21 2041.3 14.5 4.88 4.9 27.7 11.0 16.5 137.0 221319.5 70.1 4.97 3.2 3.8 6.7 2.2 132.0 23 1810.0 42.5 4.2 3.7 7.1 9.95.0. 129.0FIG. 1 depicts the evolution of the loss tangent (tan δ) under a coolingSAOS rheological experiment according to the “Crystallization via SAOSrheology” method described above. As shown in FIG. 1 and Table 12, theinventive compositions advantageously depict a high crystallizationtemperature under SAOS rheological conditions (e.g. T_(c,rheol)>131° C.and more preferably higher than 135° C.) over all comparativecompositions of the prior art. The high value of T_(c,rheol) arehypothesized to lead to faster flow/stress-induced crystallizationkinetics under fiber spinning conditions leading to more stablespinnability and favorable crystalline microstructure leading tooutstanding balance of fabric mechanical properties as described below.In FIG. 2, the corresponding profiles of the complex viscosity withtemperature for certain illustrative compositions are depicted. Withdecrease of temperature, the complex viscosity increases in a linearfunction in a log-linear plot. However, below a certain temperature, thecomplex viscosity abruptly increases due to occurrence ofcrystallization under SAOS flow.

TABLE 3 Thermal (DSC) properties of polymer compositions at a heatingand cooling rate of 1° C./min. ΔH_(cryst) Example T_(c,p) (° C.) T_(m,p)(° C.) (cal/g) SCL (° C.) SCP (° C.) 1 134.7 167.7 108.2 52.5 −19.5 2134.4 165.1 105.2 50.1 −19.4 3 131.4 166.8 106.5 51.6 −16.3 4 130.1164.7 106.4 49.7 −15.1 5 126.0 163.8 94.2 48.9 −11.1 6 134.4 167.7 105.052.4 −19.2 7 126.3 163.1 93.6 48.3 −11.5 8 126.2 163.5 113.0 48.7 −11.39 131.6 164.6 84.8 49.7 −16.7 10 122.3 170.2 91.1 54.7 −6.8 11 130.7163.4 97.1 48.5 −15.9 12 132.6 166.7 96.3 51.5 −17.5 13 115.9 152.5 88.738.7 −2.0 14 119.2 154.0 87.6 40.0 −5.3 15 116.0 152.7 82.6 38.9 −2.1 16120.7 169.1 100.8 53.7 −5.3 17 120.5 167.4 97.6 52.2 −5.3 18 126.8 164.7101.9 49.8 −11.9 19 124.7 163.5 100.3 48.7 −9.9 20 127.5 163.9 108.149.0 −12.6 21 132.51 167.1 109.6 51.9 −17.3 22 127.89 165.1 100.4 50.1−12.9 23 125 162.6 99.3 47.9 −10.2 The supercooling limit SCL iscalculated according to Eq. (11) with T_(mp) at 1° C./min. Thesupercooling parameter SCP is calculated according to Eq. (12) withT_(mp) and T_(cp) at 1° C./min.

TABLE 4 Thermal (DSC) properties of polymer compositions at a heatingand cooling rate of 10° C./min. ΔH_(cryst) Example T_(c,p) (° C.)T_(m,p) (° C.) (cal/g) SCL (° C.) SCP (° C.) 1 122.7 164.5 96.3 49.5−7.8 2 120.1 163.3 101.0 48.5 −5.3 3 120.2 164.0 110.8 49.1 −5.3 4 119.7163.6 101.4 48.8 −4.8 5 116.4 160.3 110.0 45.7 −1.9 6 123.5 163.7 106.748.9 −8.6 7 115.9 161.3 106.0 46.7 −1.3 8 118.5 161.8 106.3 47.1 −3.8 9120.4 160.3 95.6 45.7 −5.9 10 110.9 158.7 102.3 44.3 3.5 11 123.2 162.7105.7 47.9 −8.5 12 121.3 165.0 109.7 50.0 −6.3 13 109.0 149.4 89.3 35.94.5 14 107.3 151.2 90.6 37.5 6.4 15 107.4 150.9 92.4 37.3 6.3 16 109.4164.9 95.9 49.9 5.5 17 110.5 163.8 89.0 48.9 4.4 18 116.7 163.7 101.648.9 −1.9 19 116.4 164.7 99.7 49.7 −1.4 20 119.5 163.4 102.8 48.6 −4.721 121.8 162.1 101.2 47.4 −7.1 22 115.5 160.8 94.4 46.2 −0.9 23 114.2160.1 95.7 45.5 0.4 The supercooling limit SCL is calculated accordingto Eq. (11) with T_(mp) at 10° C./min. The supercooling parameter SCP iscalculated according to Eq. (12) with T_(mp) and T_(cp) at 10° C./min.

TABLE 5 Molecular weight (GPC) and intrinsic viscosity data of polymercompositions. M_(w) M_(n) M_(z) M_(v) Intrinsic (kg/ (kg/ (kg/ (kg/Viscosity Example mol) mol) mol) mol) M_(w)/M_(n) M_(z)/M_(w) (dg/l) 1204.9 71.7 367.1 184.8 2.86 1.79 1.249 2 202.9 73.8 377.8 182.7 2.752.12 1.194 3 207.1 76.1 372.6 186.9 2.72 1.80 1.198 4 5 203.9 65.6 376.7183.6 3.11 1.85 1.222 6 205.4 71.5 360.1 185.4 2.87 1.75 1.245 7 209.461.2 382.4 187.8 3.42 1.83 1.248 8 190.5 58.2 344.9 171.6 3.27 1.811.170 9 190.6 56.3 395.4 168.0 3.40 2.07 1.140 10 183.3 62.9 358.0 164.12.92 1.95 1.153 11 12 196.8 62.4 409.6 173.9 3.15 2.08 1.140 13 188.981.9 288.8 175.0 2.31 1.53 1.148 14 198.7 90.5 313.7 183.7 2.20 1.581.185 15 201.0 83.5 307.0 186.5 2.41 1.53 1.220 16 220.1 72.4 410.6197.1 3.04 1.87 1.261 17 202.5 62.2 382.3 181.1 3.26 1.89 1.212 18 220.952.3 520.9 191.0 4.23 2.36 1.239 19 195.8 53.6 359.2 175.4 3.65 1.841.161 20 226.6 56.3 628.4 195.5 4.02 2.77 1.315 21 231.7 61.1 641.1199.3 3.79 2.77 1.330 22 206.8 60.4 384.5 185.1 3.43 1.86 1.238 23 212.565.7 382.0 191.2 3.24 1.80 1.276

TABLE 6 ¹³C NMR tacticity data of polymer compositions Stereo RegioAverage % Molar Defects/ Defects/ Total Meso Meso 10,000 10,000 Defects/Run Pentads Propylene Propylene 10,000 Example Length (mmmm) MonomersMonomers Monomers 1 106.6 0.952 93 1  94 2 100.7 0.948 99 0  99 3 97.30.956 103 0 103 4 103.2 0.948 96 1  97 5 112.4 0.952 88 1  89 6 105.30.954 95 0  95 7 110.3 0.951 90 1  91 8 102.6 0.949 97 1  98 9 91.00.909 110 0  110** 10 105.3 0.952 95 0  95 11 103.0 0.952 97 0  97 12103.0 0.950 97 0  97 13 68.1 0.947 109 35 144 14 91.4 0.990 23 85 108 1581.1 0.981 44 79 122 16 67.3 0.924 149 0 149 17 60.4 0.918 164 2 166 1895.1 0.946 105 0 105 19 67.7 0.928 146 2 148 20 90.0 0.946 110 2 112 21100.0 0.955 100 0 100 22 73.0 0.928 137 0 137 23 57.0 0.910 174 0 174 *The average meso run length (MSL) is calculated according to Eq. (16).**Total defects for Example 9 represent the sum of structural chainpunctuations or defects (stereo and regio defects) per 10,000 propylenemonomers but do not include defects due to the presence of ethylene inthis sample.The above compositions are suitable for forming fibers and nonwovenfabrics. The polymer compositions 1 to 8 and 21 are suitable for makingfibers and nonwovens according to a preferred embodiment of thisinvention. The polymer compositions designated above as Examples 9, 14to 20, 22 and 23 are suitable for making fibers and nonwovens accordingto certain other embodiments of the invention. Fibers or fabricscomprising Reference Examples 10 to 13 are included for referencepurposes only.

TABLE 7 Bulk Physical properties data of certain illustrativecompositions. 1% Secant Flexural Yield Modulus Stress % Yield HDT at 66psi HDT at 264 psi Example (kpsi) (psi) Strain (° C.) (° C.) 1 210 509110.0 106.8 58.7 3 209 5022 10.0 103.3 59.6 5 218 5022 9.5 96.6 57.6 7215 5002 9.5 99.1 57.0 8 219 5076 9.5 99.4 58.1 12 213 5096 9.5 106.960.0 13 192 4663 9.2 98.3 56.6 15 199 4839 9.0 99.2 57.2 17 187 457311.4 88.5 53.5The above polymer compositions were then formed into fibers andnonwovens according to the following procedures:Fiber Spinning (Partially Oriented Yarns)Fiber spinning experiments were implemented on a Hills pilot lineequipped with a Davis Standard 1½ inches extruder and a spinneret of 72holes each of diameter of 0.60 mm. The polymer pellets were melted andextruded into a metering pump at the desired throughput rate. Melttemperature at the die was kept at 237° C. for all resins forconsistency, unless otherwise indicated. The quench air system was keptoff. Throughput per hole was set at 0.53 gr/min/hole (ghm). Two take-upspeeds were explored: 1500 and 3500 m/min as indicated. Under theseconditions, fiber denier per filament (dpf) was 3.2 and 1.4 according toEq. (17) for a take-up speed 1500 m/min and 3500 m/min, respectively.The fiber samples were drawn on a godet roll set at the desired take-upspeed and the fibers were collected on a core using a winder. Noadditional drawing step was performed. Tensile properties of the as-spunfibers are shown in Table 8.

As seen in Table 8, the inventive compositions overall give an excellentbalance of fiber tenacity and elongation to break relative tocompositions of prior art. For example, inventive composition of example5 gives significantly higher elongation to break (108%) relative tocomposition of example 15 (81%) at similar fiber tenacity for bothcompositions (˜3 g/dpf) at a fiber denier of 1.3 dpf. Inventivecomposition 21 provides unexpectedly very high fiber % elongation(˜171%) at high fiber tenacity (˜2.9 g/dpf) for 1.3 dpf.

Spinnability was assessed via a “ramp to break” experiment according towhich spinning starts at 2000 m/min and is increased at a fixedacceleration rate (480 m/min²) until fiber breakage, while all otherprocessing conditions are kept constant. The speed at which fiber breaksare observed is referred to as max spin speed. Each ramp to break testwas performed at a throughput of 0.53 ghm and 0.32 ghm. From the maxspin speed and throughput per hole, one can estimate the minimum denierper filament that can be produced for a given resin before breakageaccording to Eq. (17) above. Excellent spinnability is defined here asthe ability of a certain composition to produce fibers of minimum dpfless than about 2.0 and preferably less than about 1.5 at a throughputrange of 0.32 to 0.52 ghm. The results of the ramp to break experimentsare shown in Table 9.

As depicted in Table 9, the compositions used in Examples 1, 5, 7, 8,15, 17, 20 and 21, and especially Examples 1, 5, 7, 8 and 21, presentexcellent spinnability attested by their ability to make thin fibers ofless than about 1.5 dpf for a throughput range of 0.32-0.52 ghm.

TABLE 8 Tensile properties (tenacity and elongation at break) of POYfibers for inventive and reference examples. Tenacity % ElongationTenacity % Elongation Average dpf (g/dpf) at Break Average dpf (g/dpf)at Break (0.53 ghm, (0.53 ghm, (0.53 ghm, (0.53 ghm, (0.53 ghm, (0.53ghm, Example 1500 m/min) 1500 m/min) 1500 m/min) 3500 m/min) 3500 m/min)3500 m/min) 1 3.1 2.8 226.8 1.2 2.95 110.0 5 3.1 2.69 218.6 1.3 3.00107.9 7 3.1 2.67 196.1 1.4 2.49 91.1 8 3.1 2.66 205.2 1.3 2.93 114.9 12 3.0 2.63 211.4 1.3 2.94 96.5 13* 3.0 2.98 168.3 1.3 4.11 52.0 15  3.03.04 196.2 1.3 3.18 80.6 17  3.0 2.83 217.9 1.4 3.00 108.2 21* 2.9 2.01318.7 1.3 2.87 171.4 *The melt temperature for Examples 13 and 21 was265.5° C.

TABLE 9 Maximum (break) spin speed and minimum achievable denier perfilament (dpf) for POY fiber spinning for inventive and referenceexamples Max Spin Speed Min Max Spin Speed Min dpf (m/min) at 0.53 dpfat 0.53 (m/min) at 0.32 at 0.32 Example ghm ghm ghm ghm 1 5000 0.9 41000.7 5 4300 1.1 3500 0.8 7 3600 1.3 2500 1.2 8 4200 1.1 3400 0.8 12  50000.9 4250 0.7 13* 4500 1.0 3500 0.8 15  5000 0.9 4100 0.7 17  4900 1.04050 0.7 20  3975 1.2 2825 1.0 21* 4970 0.9 2900 1.0 *The melttemperature for Examples 13 and 21 was 265.5° C.Spunbond Nonwoven FabricsSpunbonded nonwoven fabrics were produced on a Reicofil 4 (R₄) line with3 spunbond (SSS) of about 1.1 m width each having a spinneret of about6300 holes with a hole (die) diameter of 0.6 mm. For a detaileddescription of Reicofil spunbonding process, please refer to EP 1340 843or U.S. Pat. No. 6,918,750. The throughput per hole was about 0.53 ghm.The quench air temperature was 20° C. for all experiments. The ratio ofthe volume flow VM of process air to the monomer exhaust device to theprocess air with volume flow V1 escaping from the first upper coolingchamber section into a second lower cooling chamber section (VM/V1) wasmaintained in the range of from 0.1 to 0.3. Under these conditions,partially oriented filaments of about 1 to 1.4 denier were produced,equivalent to a filament diameter of about 12 to 15 microns [Eq. (18)]above. Line speed was kept constant at 900 m/min. The filaments weredeposited continuously on a deposition web with a targeted fabric basisweight for all examples of 10 g/m² (gsm).

The formed fabric was thermally bonded by compressing it through a setof two heated rolls (calenders) for improving fabric integrity andimproving fabric mechanical properties. Fundamentals of the fabricthermal bonding process can be found in the review paper by Michielsonet al. “Review of Thermally Point-bonded Nonwovens: Materials,Processes, and Properties”, J. Applied Polym. Sci. Vol. 99, p. 2489-2496(2005) or the paper by Bhat et al. “Thermal Bonding of PolypropyleneNonwovens: Effect of Bonding Variables on the Structure and Propertiesof the Fabrics”, J. Applied Polym. Sci., Vol. 92, p. 3593-3600 (2004).The two rolls are referred to as “embossing” and S rolls. In table 10,the set temperature of the two calenders is listed corresponding to theset oil temperature used as the heating medium of the rolls. Thecalender temperature was measured on both embossing and S rolls using acontact thermocouple and was typically found to be about 10 to 20° C.lower than the set oil temperature. All three spunbonding beams hadsimilar operating conditions. Representative operating conditions aresummarized in Table 10, where Air Volume Ratio (V1/V2) is the ratio ofthe volume flow V1 escaping from the first upper cooling chamber sectionto the volume flow V2 escaping from the second lower cooling chambersection. In a typical trial, after establishing stable spinningconditions, the calender temperature was varied to create the bondingcurve (i.e., tensile strength versus calender temperature). Under theconditions of Table 10, the spinnability of the inventive and comparisoncompositions was assessed to be excellent.

In Table 11, the fabric tensile properties are summarized correspondingto the calender temperatures resulting in the maximum CD tensilestrength. At severe processing conditions of high line speed (900m/min), high throughput (˜0.53 ghm) and low basis weight (10 gsm) thatare expected to deteriorate the mechanical properties of the fabrics,most inventive fabrics surprisingly depicted high specific tensilestrength in both MD and CD directions (higher than about 2.7 N/5 cm/gsmin MD and higher than about 1.1 N/5 cm/gsm in CD). The inventive fabricshave advantageously lower tensile strength anisotropy (e.g. lower thanabout 2.6), e.g. 2.9 for the composition of example 15 and 3.2 forreference composition of reference example 13.

In Table 12, it is shown that the fabrics of the present invention leadto advantageously softer fabrics as attested by both a lower tensilemodulus (particularly MD modulus) and lower total hand.

Elmendorf tear strength for inventive and reference examples for both MDand CD directions is shown in Table 13. The fabrics of the Examples showoverall comparable or higher tear strength as compared with ReferenceExamples.

TABLE 10 Processing conditions of non-woven spunbonding fabrics ofinventive and reference examples. In all cases, 3 spunbonding beams wereused (SSS) with a line speed of 900 m/min and a nominal fabric basisweight of 10 g/m². Calender Set Melt Temperatures Temperature ThroughputCabin Air Volume For Maximum CD Filament at the Die per hole PressureRatio Tensile Strength Example Denier (° C.) (g/min/hole) (Pa) V₁/V₂ (°C.) 1 1.3 257 0.53 5300 0.12 176/165 4 1.2 257 0.52 5300 0.12 184/165 51.3 259 0.53 5300 0.13 180/165 9 1.1 260 0.52 5000 0.15 164/160 10 1.2241 0.52 7000 0.11 169/165 11 N/A 235 0.52 5500 0.15 168/164 13 1.2 2310.52 7200 0.12 162/159 15 1.3 259 0.53 5300 0.21 186/171

TABLE 11 Fabric tensile strength properties for inventive and referenceexamples. The fabric tensile data correspond to fabrics produced at thecalender set temperatures of Table 10 resulting in the maximum CDtensile strength. The line speed is 900 m/min. MD Specific CD SpecificFabric Tensile Tensile Tensile MD % CD % Basis Strength at Strength atStrength Elongation Elongation Weight Peak Load Peak Load Anisotropy atPeak at Peak Example (gsm) (N/5 cm/gsm) (N/5 cm/gsm) MD/CD Load Load 19.5 3.19 1.22 2.61 45.8 63.3 4 9.8 2.68 1.14 2.35 35.1 60.4 5 9.7 3.011.16 2.58 39.5 66.4 9 10.2 2.55 0.96 2.65 47.8 64.5 10 10.7 2.39 0.972.46 35.1 55.7 11 10.0 2.76 0.93 2.97 44.2 59.0 13 9.8 2.73 0.85 3.2324.3 39.0 15 9.9 3.35 1.14 2.93 39.0 55.3

TABLE 12 Fabric stiffness and softness related properties for inventiveand reference examples. The listed properties correspond to fabricsproduced at the calender set temperatures of Table 10 resulting in themaximum CD tensile strength. MD Tensile CD Tensile MD CD Modulus ModulusHand Hand Total Hand Example (N/5 cm/gsm) (N/5 cm/gsm) (gr) (gr) (gr) 129.0 2.8 8.65 3.63 6.14 4 26.0 2.6 9.25 4.40 6.83 5 32.1 2.4 8.55 3.706.13 9 23.8 1.9 7.75 3.03 5.39 10 23.8 2.5 8.70 3.33 6.01 11 28.9 2.59.05 3.83 6.44 13 37.1 3.5 10.28 3.65 6.96 15 36.2 2.8 9.88 3.90 6.89

TABLE 13 Fabric Elmedorf tear strength for inventive and referenceexamples. The listed properties correspond to fabrics produced at thecalender set temperatures of Table 10 resulting in the maximum CDtensile strength. MD Elmendorf Tear Strength CD Elmendorf Tear StrengthExample (gr/gsm) (gr/gsm) 1 10.7 17.2 4 8.7 15.0 5 9.9 13.5 9 8.5 13.710 7.5 16.0 11 N/A N/A 13 12.8 16.5 15 11.5 16.7Additional Fabric Properties

Tear properties of fabrics on tongue-shaped test pieces, was determinedby DIN EN ISO 13937-4. Nonwoven tear resistance was determined by DIN ENISO 9073-4. Determination of breaking strength and elongation ofnonwoven materials using the grab tensile test was obtained according toDIN EN ISO 9073-18. The bursting strength of fabrics, pneumatic methodof determination of bursting strength and bursting distension, wasdetermined according to DIN EN ISO 13938-2. Abrasion resistance offabrics was determined by the by the Martindale method. Specimenbreakdown was determined according to DIN EN ISO 12947-2. Nonwovenbending length was determined by DIN EN ISO 9073-7. Drapability ofnonwovens, including drape coefficient, was determined by DIN EN ISO9073-9.

Three polymer compositions, a polymer having an MFR of 16.5 made usingthe same procedure as Example 1 (referred to as EX1-A), Lumicene™ MR2002and PP3155, were formed into nonwoven fabrics according to the generalprocedure for Spunbond Nonwoven Fabrics detailed above including that 3spunbonding beams were used (SSS) with a line speed of 900 m/min and anominal fabric basis weight of 10 g/m². Specific process conditions arelisted in Table A below.

TABLE A Processing conditions of non-woven spunbonding fabrics. In allcases, 3 spunbonding beams were used (SSS) with a line speed of 900m/min and a nominal fabric basis weight of 10 g/m². Calender Set MeltTemperatures Filament Temperature Throughput Cabin Air Volume ForMaximum CD Denier at the Die per hole Pressure Ratio Tensile StrengthExample Resin (dpf) (° C.) (g/min/hol) (Pa) V₁/V₂ (° C.) A-1 EX1-A 1.3258 0.53 5300 0.14 180/165 A-2 Lumicene 1.3 259 0.53 5300 0.21 182/171MR 2002 A-3 EX1-A N/A 245 0.53 4500 0.25 168/165 A-4 Lumicene 1.4 2590.53 5300 0.21 176/171 MR 2002 A-5 PP3155 1.4 235 0.53 5500 0.25 168/164

Grab Tensile data, reported in Table B below were obtained according tothe procedure in DIN EN 9073-18. Tongue tear data, reported in Table C,were determined according to DIN EN ISO 9073-4. Burst strength, reportedin Table C, were obtained according to ISO 13938-2 1999.

TABLE B Grab Tensile Properties MD Grab MD Grab MD Length MD % CD GrabCD Grab CD Length CD % Fabric Basis Tensile Tensile Change at ElongationTensile Tensile Change at Elongation Weight Peak Load Peak Load PeakLoad at Peak Peak Load Peak Load Peak Load at Peak Example (gsm) (N)(N/gsm) (mm) Load (N) (N/gsm) (mm) Load A-1 9.8 40.64 4.15 35.1 46.521.05 2.15 58.4 76.3 A-2 9.8 41.53 4.24 29.8 39.5 20.7 2.11 57.8 75.6A-3 9.8 37.53 3.83 33.7 44.7 19.04 1.94 52.6 69.1 A-4 9.7 42.92 4.4232.1 42.6 21.07 2.17 50.3 66.1 A-5 10.4 34.65 3.33 31.7 42.1 18.24 1.7552.1 67.9

TABLE C Tongue Tear and Burst Strength MD Tear Bursting Burst CD TearMax Max Force Strength Height Example Force (N) (N) (kPa) (mm) A-1 9.27.8 28.5 31.1 A-2 9.3 8.0 21.8 28.5 A-3 9.4 8.8 31.0 32.5 A-4 9.4 9.131.9 30.7 A-5 7.8 5.8 26.9 31.8

A polymer having an MFR of 16.5 made using the same procedure as Example1 (referred to as EX1-A), Achieve™ 3854, and Lumicene™ MR 2002 wereformed into fabrics and then tested for various physical properties. Thedata are reported in Tables D and E. Achieve™ 3854 is a metallocenepropylene homopolymer having a MFR of 24 dg/min available fromExxonMobil Chemical Company, Houston Tex. Lumicene™ MR 2002 is ametallocene propylene homopolymer having a melt flow index (230° C.,2.16 kg ISO 1133) of 15 about dg/min and a Tm of about 153° C. availablefrom Total Petrochemicals, Feluy Belgium. The fabrics were formed by thespunbonded nonwoven fabric process and conditions described above at anominal fabric basis weight of 10 gsm, except that fabrics produced at aline speed of 300 m/min used one spunbond beam.

TABLE D Fabric tensile properties per WSP 110.4 (05) at low (300 m/min)and high (900 m/min) spunbond line speed conditions. Fabric Tensiletesting conditions: basis CD Peak MD Peak 100 m/min, 200 mm gauge weightCD Strength MD Strength Elongation Elongation length (gsm) (N/5 cm/gsm)(N/5 cm/gsm) (%) (%) PP3155 (300 m/min) 10.1 1.27 2.35 51. 42.9 PP3155(900 m/min) 10.3 0.95 2.76 59.0 44.2 Achieve ™ 3854 (300 m/min) 10.01.32 3.14 45.5 40.4 Achieve ™ 3854 (900 m/min) 9.8 0.85 2.73 39.0 24.3EX1-A(300 m/min) 10.2 1.61 2.52 56.7 45.3 EX1-A(900 m/min) 9.8 1.13 2.8938.4 Lumicene ™ MR 2002 (300 m/min) 10 1.70 2.92 50.3 44.6 Lumicene ™ MR2002 (900 m/min) 9.8 1.21 3.33 37.7 US 20110081817 Example 3* 12.0 1.62.9 59 65.0 US 20110081817 Example 4* 12.0 1.65 3.03 66 68.0 US20110081817 12.0 1.49 2.82 57 56.0 Comparative Example 2* US 20100233927Example 2* 12.0 1.78 3.18 69.4 66.9 US 20110059668 Example 3* 12.0 1.302.85 66 61.0 *data taken from cited reference, 300 m/min

TABLE E Fabric Elmendorf tear strength (ASTM D 1922) at low (300 m/min)and high (900 m/min) spunbond line speed conditions, nominal Fabricbasis weight 10 gsm CD Elmendorf CD Elmendorf CD Elmendorf MD ElmendorfCD Elmendorf CD Elmendorf Tear (N/gsm) CD Elmendorf CD Elmendorf Tear(N/gsm) Tear (gr/gsm) Tear (gr/gsm) speed Tear (N/gsm) Tear (N/gsm)Lumicene Tear (N/gsm) Tear (N/gsm) Lumicene Achieve Achieve (m/min)PP3155 EX1-A MR 2002 PP3155 EX1-A MR 2002 3854 3854 300 11.8 15.9 20.57.8 11.0 14.7 19.4 13.1 900 12.7 13.1 16.1 7.0 9.6 11.6 16.5 12.8

All documents described herein are incorporated by reference herein,including any priority documents and/or testing procedures to the extentthey are not inconsistent with this text, provided however that anypriority document not named in the initially filed application or filingdocuments is NOT incorporated by reference herein. As is apparent fromthe foregoing general description and the specific embodiments, whileforms of the invention have been illustrated and described, variousmodifications can be made without departing from the spirit and scope ofthe invention. Accordingly, it is not intended that the invention belimited thereby. Likewise, the term “comprising” is consideredsynonymous with the term “including” for purposes of Australian law.Likewise whenever a composition, an element or a group of elements ispreceded with the transitional phrase “comprising”, it is understoodthat we also contemplate the same composition or group of elements withtransitional phrases “consisting essentially of,” “consisting of”,“selected from the group of consisting of,” or “is” preceding therecitation of the composition, element, or elements and vice versa.

What is claimed is:
 1. A nonwoven fabric comprising polypropylene fibershaving a denier per filament (dpf) value of 0.3 to 5 dpf, wherein saidpolypropylene fibers comprise a visbroken propylene polymer compositioncomprising at least 50 mol % propylene, said polymer composition having:a) a melt flow rate (MFR, ASTM 1238, 230° C., 2.16 kg) of 10 to 25dg/min; b) a dimensionless Stress Ratio/Loss Tangent Index R₂ [definedby Eq. (8) below] at 190° C. from 1.5 to 30; $\begin{matrix}{R_{2} = {\left( \frac{{{SR}\left( {500\mspace{14mu} s^{- 1}} \right)}\eta_{o}}{\tan\;{\delta\left( {0.1\mspace{14mu}{rad}\text{/}s} \right)}} \right)/248}} & (8)\end{matrix}$ where η_(o) [Eq. (1) below] is in Pa s; $\begin{matrix}{\eta_{o} = {\sum\limits_{j = 1}^{M}{\lambda_{j}G_{j}}}} & (1)\end{matrix}$ c) an onset temperature of crystallization under flow,T_(c,rheol), (as determined by SAOS rheology, 1° C./min, where saidpolymer has 0 wt % nucleating agent present), of at least 123° C.; d) anaverage meso run length determined by ¹³C NMR of at least 55 or higher;and e) a peak melting temperature Tmp of at least 160° C.
 2. A nonwovenfabric according to claim 1, said nonwoven fabric being obtainable byspun-bonding with a production line speed of at least 400 m/min.
 3. Anonwoven fabric according to claim 1, wherein said fabric has a fabrictensile anisotropy as defined herein of less than 3.0 when produced at aproduction line speed of 900 m/min.
 4. A laminate nonwoven fabriccomprising a first nonwoven and a second nonwoven, each of said firstand second nonwovens being independently selected from spunbondednonwovens and meltblown nonwovens, wherein at least one of saidnonwovens comprises a nonwoven fabric according to claim
 1. 5. Anonwoven fabric according to claim 1, obtainable by spunbonding with aline speed of at least 600 m/min.
 6. A laminate fabric comprising anonwoven fabric according to claim 1 and at least one or more furtherfabric layers, said one or more further fabric layers being selectedfrom body fluid impermeable layers and body fluid permeable layers.
 7. Anonwoven according to claim 1, wherein the fibers comprise a yarncomprising a plurality of polypropylene filaments having a dpf value offrom 0.3 to 5 dpf.
 8. A nonwoven fabric according to claim 1, having afabric basis weight in the range of 5 to 70 gsm.
 9. A nonwoven fabricaccording to claim 1, said nonwoven fabric is obtainable by spunbondingwith a production line speed of at least 400 m/min.
 10. A nonwovenaccording to claim 1, wherein the fibers comprise monofilaments of 0.3to 5 denier.
 11. An article comprising a one or more nonwoven fabricsaccording to claim
 1. 12. A diaper comprising one or more nonwovenfabrics according to claim 1.